Background

Myeloproliferative Neoplasms

MPNs are rare overlapping blood diseases characterized by the production of one or more blood cell lines. The most common forms of MPNs include polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), and chronic myeloid leukemia. A common finding in many MPNs is clonality and a central pathogenic feature the detection of a somatic (acquired) pathogenic variant in disease-associated genes. Pathogenic variants in disease-associated genes result in constitutively activated tyrosine kinase enzyme or cell surface receptor.

The paradigm for the use of molecular genetics to revolutionize patient management is chronic myeloid leukemia. A unique chromosomal translocation t (9;22), the Philadelphia chromosome (Ph), leads to a unique gene rearrangement (BCR-ABL) creating a fusion gene that encodes for a constitutively active Bcr-abl fusion protein. These findings led to the development of targeted tyrosine kinase inhibitor drug therapy (imatinib) that produces long-lasting remissions. Rare patients may show unusual manifestations of nonclassic forms of MPNs, such as chronic myelomonocytic leukemia, hypereosinophilic syndrome, systemic mastocytosis, chronic neutrophilic leukemia, or others. Reports have identified JAK2 V617F variants in some of these cases.^1,[10]The remainder of this policy focuses only on the non-Ph or Ph-negative MPNs and genetic testing for JAK2, CALR, and MPL.

Diagnosis and monitoring of patients with Ph-negative MPNs have been challenging because many of the laboratory and clinical features of the classic forms of these diseases can be mimicked by other conditions such as reactive or secondary erythrocytosis, thrombocytosis, or myeloid fibrosis. Additionally, these entities can be difficult to distinguish on morphologic bone marrow exam, and diagnosis can be complicated by changing disease patterns: PV and ET can evolve into PMF or undergo a leukemic transformation. A complex set of clinical, pathologic, and biologic criteria was first introduced by the Polycythemia Vera Study Group in 1996^2,3, and by the World Health Organization as a benchmark for diagnosis in 2002^4, and updated in 2008 and 2016.^5,6, Applying these criteria has been challenging because they involve complex diagnostic algorithms, rely on amorphologic assessment of uncertain consistency, and require tests that are not well-standardized or widely available, such as endogenous erythroid colony formation. An important component of the diagnostic process is a clinical and laboratory assessment to rule out reactive or secondary causes of disease.

Chronic Myeloid Leukemia and Philadelphia Chromosome

Ph-Negative MPNs

Classic MPNs

Varying combinations of these criteria are used to determine whether a patient has PV, ET, or PMF, i.e., MPNs that are Ph-negative. An important component of the diagnostic process is a clinical and laboratory assessment to rule out reactive or secondary causes of disease.

As noted, some diagnostic methods (e.g., bone marrow microscopy) are not well-standardized,^7,8,9, and others (e.g., endogenous erythroid colony formation) are neither standardized nor widely available.

Nonclassic Forms of MPNs

Although the most common Ph-negative MPNs include what is commonly referred to as classic forms of this disorder (PV, ET, PMF). Rare patients may show unusual manifestations of nonclassic forms of MPNs, such as chronic myelomonocytic leukemia, hypereosinophilic syndrome, systemic mastocytosis, chronic neutrophilic leukemia, or others. Reports have identified JAK2 V617F variants in some of these cases.^1,

Molecular Genetics of Ph-Negative MPNs

JAK2 Gene

The JAK2 gene, located on chromosome 9, contains the genetic code for making the Janus kinase 2 protein, a nonreceptor tyrosine kinase. The Janus kinase 2 (JAK2) protein is part of the JAK/signal transduction pathway and activators of transcript (STAT) proteins that are important for the controlled production of blood cells from hematopoietic cells. Somatic (acquired) variants in the JAK2 gene are found in patients with PV, ET, and PMF.^10,

JAK2 V617F Variant

In 2005, 4 separate groups using different modes of discovery and different measurement techniques reported on the presence of a novel somatic (acquired) single nucleotide variant in the conserved autoinhibitory pseudokinase domain of the gene encoding JAK2 protein in patients with classic MPNs. The single nucleotide variant caused a valine-to-phenylalanine substitution at amino acid position 617 (JAK2 V617F) leading to a novel somatic gain-of-function single nucleotide variant that resulted in the loss of autoinhibition of the JAK2 tyrosine kinase. JAK2 V617F is a constitutively activated kinase that recruits and phosphorylates substrate molecules including STAT proteins (so-called JAK-STAT signaling). The result is cell proliferation independent of normal growth factor control.

The JAK2 V617F variant was present in blood and bone marrow from a variable portion of patients with classic BCR-ABL-negative (i.e., Ph-negative) MPNs including 65% to 97% of patients with PV, 23% to 57% with ET, and 35% to 56% with PMF (see Table 1). The variant was initially reported to be absent in all normal subjects and patients with secondary erythrocytosis,^{9,1,11,12,13,14,15,16,17,18,19,} although very low levels of cells carrying the variant have been reported in a small subset of healthy individuals.^20,21,

Although almost all studies were retrospective case series and/or cross-sectional studies, and although both the analytic and clinical performances appeared dependent on the laboratory method used to detect the variant, there has been consistency across studies in demonstrating that the JAK2 V617F variant is a highly specific marker for clonal evidence of an MPN.

Table 1. Frequency of the JAK2 V617FVariant in Patients With Classic Philadelphia Chromosome-Negative Myeloproliferative Neoplasm From Case Series

Study	Variant Detection Method	PV	ET	PMF	Normals	Secondary Erythrocytosis
Baxter et al (2005)9,	DNA sequencing, PCR	71/73 (97)	29/51 (57)	8/16 (50)	0/90 (0)	NR
Jones et al (2005)1,	PCR testing	58/72 (81)	24/59 (41)	15/35 (43)	0/160 (0)	0/4 (0)
Levine et al (2005)11,	DNA sequencing	121/164 (74)	37/115 (32)	16/46 (35)	0/269 (0)	NR
James et al (2005)12,	DNA sequencing	40/45 (88)	9/21 (43)	3/7 (43)	0/15 (0)	0/35 (0)
Kralovics et al (2005)13,	DNA sequencing	83/128 (65)	21/94 (23)	13/23 (56)	0/142 (0)	0/11 (0)
Tefferi et al (2005)14,	PCR testing	36/38 (95)	12/46 (55)	3/10 (30)	NR	0/19 (0)
Zhao et al (2005)15,	DNA sequencing	20/24 (83)	NR	NR	0/12 (0)	NR
Campbell et al (2005)16,	PCR testing	NR	414/776 (53)	NR	NR	NR
Wolanskyj et al (2005)17,	PCR testing	NR	73/150 (49)	NR	NR	NR
Campbell et al (2006)18,	PCR testing	NR	NR	83/152 (55)	NR	NR
Tefferi et al (2005)19,	PCR testing	NR	NR	80/157 (51)	NR	NR

Values are n/N (%).

ET: essential thrombocythemia; NR: not reported; PCR: polymerase chain reaction; PMF: primary myelofibrosis; PV: polycythemia vera.

In vivo, mice irradiated and then given transplanted bone marrow cells infected with a retrovirus containing the variant developed a myeloproliferative syndrome.^12,

JAK2 Exon 12 Variants

Scott et al (2007) identified 4 somatic gain-of-function variants in JAK2 exon 12 in 10 of 11 PV patients without the JAK2 V617F variant.^22, Patients with a JAK2 exon 12 variant differed from those with the JAK2 V617F variant, presenting at a younger age with higher hemoglobin levels and lower platelet and white cell counts. Erythroid colonies could be grown from their blood samples in the absence of exogenous erythropoietin, and mice treated with transfected bone marrow transplants developed a myeloproliferative syndrome.

Findings have been confirmed by a number of investigators who identified additional variants with similar functional consequences in patients with PV and patients with idiopathic erythrocytosis.^23,24, Based on these findings, it has been concluded that the identification of JAK2 exon 12 variants provides a diagnostic test for JAK2 V617F-negative patients who present with erythrocytosis. Of note, different variants in the same gene appear to have different effects on signaling, resulting in distinct clinical phenotypes.^22,

MPL Gene

The MPL gene, located on chromosome 1, contains the genetic code for making the thrombopoietin receptor, a cell surface protein that stimulates the JAK/STAT signal transduction pathway. The thrombopoietin receptor is critical for the cell growth and division of megakaryocytes, which produce platelets involved in blood clotting. Somatic variants in the MPL gene are associated with ET and PMF.

CALR Gene

The CALR gene, located on chromosome 19, contains the genetic code for making the calreticulin protein, a multifunctional protein located in the endoplasmic reticulum, cytoplasm, and cell surface. The calreticulin protein is thought to play a role in cell growth and division and regulation of gene activity. Somatic variants in the CALR gene are associated with ET and PMF.

Frequency of JAK2, CALR, and MPL Somatic Variants in Ph-Negative MPNs

Ph-negative MPNs are characterized by their molecular genetic alterations. Table 2 summarizes the driver genes and somatic variants associated with specific Ph-negative MPNs.^25,

Table 2. Frequency of JAK2, CAL4, and MPL Somatic Variants in Ph-Negative MPNs

Ph-Negative MPNs	JAK2 Somatic Variant Detected, % of Patients	CALR Somatic Variant Detected, % of Patients	MPL Somatic Variant Detected, % of Patients
Polycythemia vera	JAK2 V617F, 95 JAK2 exon 12 variants, 5
Essential thrombocythemia	JAK2 V617F, 60-65	CALR exon 9 indels, 20-25	MPL exon 10 variants, 5
Primary myelofibrosis	JAK2 V617F, 60-65	CALR exon 9 indels, 20-25	MPL exon 10 variants, 5

Adapted from Cazzola et al (2014).^25,
indels: insertions and deletions; MPN: myeloproliferative neoplasm; Ph: Philadelphia chromosome.

Regulatory Status

Clinical laboratories may develop and validate tests in-house and market them as a laboratory service; laboratory-developed tests must meet the general regulatory standards of the Clinical Laboratory Improvement Amendments. More than a dozen commercial laboratories currently offer a wide variety of diagnostic procedures for JAK2, CALR, and MPL testing under the auspices of the Clinical Laboratory Improvement Amendments. Laboratories that offer laboratory-developed tests must be licensed by the Clinical Laboratory Improvement Amendments for high-complexity testing. To date, the U.S. Food and Drug Administration has chosen not to require any regulatory review of this test.

Related Policies

• None

NOTE: For Medicare Advantage, Medicaid and FIDE-SNP, please refer to the Coverage Sections below for coverage guidance.)

1. JAK2 testing is considered medically necessary in the diagnosis of members presenting with clinical, laboratory, or pathological findings suggesting polycythemia vera, essential thrombocythemia, or primary myelofibrosis. Based on criteria from the World Health Organization, documentation of a serum erythropoietin level below the reference range for normal is recommended before JAK2 testing (See Policy Guidelines).

2. MPL and CALR testing is considered medically necessary in the diagnosis of members presenting with clinical, laboratory, or pathologic findings suggesting essential thrombocythemia or primary myelofibrosis.

3. JAK2, MPL, and CALR testing are considered investigational in all other circumstances including, but not limited to, the following situations:

• Diagnosis of nonclassic forms of myeloproliferative neoplasms
• Molecular phenotyping of members with myeloproliferative neoplasms
• Monitoring, management, or selecting treatment in members with myeloproliferative neoplasms.

Testing strategy
Patients suspected to have polycythemia vera should first be tested for the most common finding, JAK2 V617F. If the testing is negative, further testing to detect other JAK2 tyrosine kinase variants (e.g., in exon 12) is warranted.

Patients suspected to have essential thrombocythemia or primary myelofibrosis should first be tested for JAK2 variants, as noted. If testing is negative, further testing to detect MPL and CALR variants is warranted.

Criteria for Polycythemia Testing
Based on the World Health Organization (WHO) major and minor criteria (see Table PG1), documentation of serum erythropoietin level below the reference range for normal meets a minor criterion for polycythemia vera. Therefore, serum erythropoietin testing is recommended before JAK2 testing.

Table PG1. WHO Diagnostic Criteria for Polycythemia Vera

Major Criteria

Increased hemoglobin level (>16.5 g/dL in men or >16.0 g/dL in women)

Increased hematocrit (>49% in men or >48% in women)

Other evidence of increased red cell volume

Bone marrow biopsy showing hypercellularity for age with trilineage maturation, including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes (differences in size)

JAK2 V617F or JAK2 exon 12 variant detected

Minor Criterion

Serum erythropoietin level below the reference range for normal

Adapted from Arber et al (2016).
WHO: World Health Organization.

Genetics Nomenclature Update
The Human Genome Variation Society nomenclature is used to report information on variants found in DNA and serves as an international standard in DNA diagnostics. It is being implemented for genetic testing medical policy updates starting in 2017 (see Table PG2). The Society’s nomenclature is recommended by the Human Variome Project, the HUman Genome Organization, and by the Human Genome Variation Society itself.

The American College of Medical Genetics and Genomics and the Association for Molecular Pathology standards and guidelines for interpretation of sequence variants represent expert opinion from both organizations, in addition to the College of American Pathologists. These recommendations primarily apply to genetic tests used in clinical laboratories, including genotyping, single genes, panels, exomes, and genomes. Table PG3 shows the recommended standard terminology“pathogenic,” “likely pathogenic,” “uncertain significance,” “likely benign,” and “benign”to describe variants identified that cause Mendelian disorders.

Table PG2. Nomenclature to Report on Variants Found in DNA

Previous	Updated	Definition
Mutation	Disease-associated variant	Disease-associated change in the DNA sequence
	Variant	Change in the DNA sequence
	Familial variant	Disease-associated variant identified in a proband for use in subsequent targeted genetic testing in first-degree relatives

Table PG3. ACMG-AMP Standards and Guidelines for Variant Classification

Variant Classification	Definition
Pathogenic	Disease-causing change in the DNA sequence
Likely pathogenic	Likely disease-causing change in the DNA sequence
Variant of uncertain significance	Change in DNA sequence with uncertain effects on disease
Likely benign	Likely benign change in the DNA sequence
Benign	Benign change in the DNA sequence

ACMG: American College of Medical Genetics and Genomics; AMP: Association for Molecular Pathology.

Genetic Counseling
Experts recommend formal genetic counseling for patients who are at risk for inherited disorders and who wish to undergo genetic testing. Interpreting the results of genetic tests and understanding risk factors can be difficult for some patients; genetic counseling helps individuals understand the impact of genetic testing, including the possible effects the test results could have on the individual or their family members. It should be noted that genetic counseling may alter the utilization of genetic testing substantially and may reduce inappropriate testing; further, genetic counseling should be performed by an individual with experience and expertise in genetic medicine and genetic testing methods.


Medicare Coverage:
There is no National Coverage Determination (NCD) for JAK2, MPL, and CALR Testing for Myeloproliferative Neoplasms. In the absence of an NCD, coverage decisions are left to the discretion of Local Medicare Carriers. Novitas Solutions, Inc, the Local Medicare Carrier for jurisdiction JL, has established limited coverage for this service. CPT code 81270 and CPT code 81219 are covered when LCD L35396 criteria is met. Please refer to Novitas Solutions Inc, Biomarkers for Oncology (L35396) for eligibility and coverage. Available to be accessed at Novitas Solutions, Inc., Medical Policy Search page: https://www.novitas-solutions.com/webcenter/portal/MedicareJL/LcdSearch?_afrLoop=90769712476969#!%40%40%3F_afrLoop%3D90769712476969%26centerWidth%3D100%2525%26leftWidth%3D0%2525%26rightWidth%3D0%2525%26showFooter%3Dfalse%26showHeader%3Dfalse%26_adf.ctrl-state%3D63y7eftob_46.

Medicaid Coverage:
For members enrolled in Medicaid and NJ FamilyCare plans, Horizon BCBSNJ applies the above medical policy.

FIDE-SNP Coverage:
For members enrolled in a Fully Integrated Dual Eligible Special Needs Plan (FIDE-SNP): (1) to the extent the service is covered under the Medicare portion of the member’s benefit package, the above Medicare Coverage statement applies; and (2) to the extent the service is not covered under the Medicare portion of the member’s benefit package, the above Medicaid Coverage statement applies.

[RATIONALE: This policy was created in 2010 and has been updated regularly searches of the PubMed database. The most recent literature update was performed through June 10, 2019.

Evidence reviews assess whether a medical test is clinically useful. A useful test provides information to make a clinical management decision that improves the net health outcome. That is, the balance of benefits and harms is better when the test is used to manage the condition than when another test or no test is used to manage the condition.

The first step in assessing a medical test is to formulate the clinical context and purpose of the test. The test must be technically reliable, clinically valid, and clinically useful for that purpose. Evidence reviews assess the evidence on whether a test is clinically valid and clinically useful. Technical reliability is outside the scope of these reviews, and credible information on technical reliability is available from other sources.

JAK2 Testing for a Suspected Myeloproliferative Neoplasm

Clinical Context and Test Purpose

The purpose of JAK2 testing of individuals with a suspected MPN is to establish a molecular genetic diagnosis of MPN to inform management decisions.

The question addressed in this policy is: In individuals with a suspected MPN, does the use of JAK2 testing improve the net health outcome?

The following PICOs were used to select literature to inform this policy.

Patients

The relevant population of interest includes individuals with a suspected MPN.

Patients with suspected MPN are actively managed by hematologists and oncologists.

Interventions

The test being considered is genetic testing for JAK2.

Comparators

The following practice is currently being used to make decisions about individuals with a suspected MPN: standard clinical management without genetic testing.

Outcomes

The potential beneficial outcomes of primary interest include establishing a molecular genetic diagnosis of polycythemia vera (PV), essential thrombocythemia (ET), or primary myelofibrosis (PMF) to inform management decisions when test results are provided.

The time frame for outcomes measures varies from several months for the improvement of symptoms to long-term survival as a result of disease-related complications.

Technically Reliable

Assessment of technical reliability focuses on specific tests and operators and requires a review of unpublished and often proprietary information. Review of specific tests, operators, and unpublished data are outside the scope of this policy and alternative sources exist. This policy focuses on clinical validity and clinical utility.

Clinically Valid

A test must detect the presence or absence of a condition, the risk of developing a condition in the future, or treatment response (beneficial or adverse).

Mejia-Ochoa et al (2019) conducted a systematic review and meta-analysis of the frequency of JAK2, CALR, and MPL in Philadelphia chromosome (Ph)-negative chronic MPNs. Twenty studies reported the frequency of JAK2V617F in PV, ET, and PMF. The studies were heterogeneous with regard to the diagnostic techniques used and their results. The proportion of patients with JAK2V617F ranged from 46.7% to 100% in patients with PV, from 31.3% to 72.1% in patients with ET, and from 25.0% to 85.7% in those with PMF.

The World Health Organization (WHO;2016) criteria specifically recommended testing for JAK2 exon 12 variants in patients with suspected PV (presumably in patients who are JAK2 V617F-negative). The criteria suggested testing for JAK2 V617 in patients with ET.^6,

Section Summary: Clinically Valid

Evidence of the clinical validity of JAK2 V617F and exon 12 variant testing includes prospective studies and case series and a systematic review of these studies. In PV patients, the proportion of patients with JAK2V617F ranged from 46.7% to 100% in patients with PV, from 31.3% to 72.1% in patients with ET, and from 25.0% to 85.7% in those with PMF. Additionally, the WHO(2016) diagnostic criteria incorporated the JAK2 V617F variants for PV, ET, and PMF and JAK2 exon 12 variants for PV.

Clinically Useful

A test is clinically useful if the use of the results informs management decisions that improve the net health outcome of care. The net health outcome can be improved if patients receive correct therapy, or more effective therapy, or avoid unnecessary therapy, or avoid unnecessary testing.

Direct Evidence

Direct evidence of clinical utility is provided by studies that have compared health outcomes for patients managed with and without the test. Because these are intervention studies, the preferred evidence would be from randomized controlled trials (RCTs).

Testing for JAK2 V617F or JAK2 exon 12 variants have potential clinical utility in several different clinical scenarios:

1. Diagnosis of patients with clinical, laboratory, or pathologic findings suggesting classic MPNs (PV, ET, or PMF);
2. Phenotyping of disease subtypes in patients with MPNs to establish disease prognosis;
3. Identification, selection, and monitoring of treatment.

Due to the strong epidemiologic and biologic literature linking JAK2 pathway variants to the occurrence of MPNs, there has been considerable recent attention on using JAK2 as a molecular target for drug discovery. In preclinical and early clinical studies, a number of promising JAK2 inhibitors have been identified, and reports have suggested that some are useful in symptom relief.^26, Many patients with these diseases have good responses to cytotoxic drugs, and the natural course of the disease, particularly for PV and ET, can be quite indolent. Considerable study will be required to sort through the safety and efficacy of these new treatments before they enter routine clinical use. Several early-phase and preliminary treatment trials evaluating the safety and efficacy of tyrosine kinase inhibitors in patients with JAK2 V617F-positive MPNs have been reported.^27,28,29, It also has been noted that benefits from tyrosine kinase therapy may not be specific for JAK2 V617F-positive MPNs but may be observed in wild-type disease as well.^30,

In 2011, ruxolitinib (a JAK kinase inhibitor) was approved by the U.S. Food and Drug Administration for the treatment of intermediate- and high-risk myelofibrosis (including primary myelofibrosis, post-polycythemia vera myelofibrosis, and postessential thrombocythemia myelofibrosis) based on results from 2 RCTs. One, a double-blind RCT by Verstovsek et al (2012) assessing patients with intermediate- to high-risk myelofibrosis, randomized participants to twice-daily oral ruxolitinib (n=155) or to placebo (n=154) and followed them for 76 weeks (Controlled Myelofibrosis Study with Oral JAK Inhibitor Treatment [COMFORT-I]).^31, The primary outcome (a ≥35% reduction in spleen volume at or after 24 weeks) was observed in 41.9% of patients treated with ruxolitinib compared with 0.7% in the placebo group (p<0.001). At the prospectively defined data cutoff of 32 weeks, there were 10 (6.5%) deaths in the ruxolitinib group and 14 (9.1%) deaths in the placebo group (Kaplan-Meier method, p=0.33). With 4 additional months of follow-up (median, 51 weeks total follow-up), there were 13 (8.4%) total deaths in the ruxolitinib group and 24 (15.6%) total deaths in the placebo group (Kaplan-Meier method, p=0.04). Myelofibrosis symptom score at 24 weeks improved 45.9% from baseline in patients who received ruxolitinib and 5.3% in placebo patients. Discontinuations due to adverse events were similar in the ruxolitinib (11%) and placebo (10.6%) groups. In a post hoc subgroup analysis of patients with the JAK2 V617F variant, mean changes in spleen volume at 24 weeks were -34.6% in the ruxolitinib group and +8.1% in the placebo group; in patients without the variant, mean changes in spleen volume were -23.8% and +8.4%, respectively. Changes in total symptom score at 24 weeks in patients with the JAK2 V617F variant were -52.6% in the ruxolitinib group and +42.8% in the placebo group (higher scores indicate more severe symptoms); in patients without the variant, changes in total symptom score were -28.1% and +37.2%, respectively.

A second trial by Harrison et al (2012) reached similar conclusions (COMFORT-II).^32, Patients with intermediate- or high-risk primary myelofibrosis, postpolycythemia vera myelofibrosis, or postessential thrombocythemia myelofibrosis received oral ruxolitinib (n=146) or best available therapy (n=73). No differences in overall survival (OS) were observed between the 2 groups at 48 weeks. Twenty-eight percent of patients in the ruxolitinib group had at least a 35% reduction in spleen volume at 48 weeks compared with 0% in the control group (p<0.001). In the JAK2 V617F-positive subgroup, the incidence of spleen reduction was 33% in the ruxolitinib group and 0% in the control group; in the JAK2 V617F-negative subgroup, the incidence of spleen reduction was 14% in the ruxolitinib group and 0% in controls. In the ruxolitinib group, patients had an improved overall quality of life and a reduction in myelofibrosis symptoms compared with no benefit to the control group. Serious adverse events were similar between groups: anemia occurred in 5% of patients in the ruxolitinib group and 4% of the control group, pneumonia occurred in 1% of the ruxolitinib group and 5% of the control group, and 8% of patients in the ruxolitinib group and 5% in the control group discontinued treatment.

A follow-up to the COMFORT-I trial, published by Verstovsek et al (2015), provided data on a median 3-year follow-up.^33, At a median of 149 weeks (range, 19-175 weeks), 77 (49.7%) of the 155 patients originally randomized to ruxolitinib were still receiving therapy. One hundred eleven of 154 patients who originally received placebo crossed over to receive ruxolitinib, and, of these, 57 (51.4%) were still receiving the drug. Of the patients originally randomized to therapy, discontinuation rates were 21% at 1 year, 35% at 2 years, and 51% at year 3. Reasons for discontinuing ruxolitinib were disease progress (23.1%), adverse events (19.2%), death (19.2%), and withdrawal of consent (15.4%). The initial primary outcome measure of this study was a reduction in spleen volume, and, in this follow-up study, reductions in spleen size were durable with longer-term treatment. Mean percentage change from baseline was -31.6% at week 24 and -34.1% at week 144. Of patients initially randomized to ruxolitinib, 91 (59%) of 155 of patients achieved a 35% or more reduction in spleen volume at any time during study follow-up. The probability of maintaining this same reduction for at least 132 weeks was 0.53, and more than 80% of patients maintained a reduction of at least 10%. Regarding OS, 42 patients randomized to ruxolitinib died while 54 in the placebo group died. With a median follow-up of 149 weeks for both the ruxolitinib and placebo groups, the hazard ratio for (OS) favored patients in the ruxolitinib arm (hazard ratio, 0.69; 95% confidence interval, 0.46 to 1.03; p=0.067). Anemia and thrombocytopenia were the most common adverse hematologic events and were highest during the first six months of therapy, both of which subsequently increased to a new steady state. The most common nonhematologic adverse events, which occurred more commonly in the ruxolitinib group, were ecchymosis (18.7%), dizziness (14.8%), and headache (14.8%). Additionally, more patients treated with study drug developed urinary tract infections and herpes zoster, although the incidence of these infections did not increase with the length of therapy. All herpes zoster infections were grade 1 or 2, and no other opportunistic infections were identified during follow-up. Four new cases of acute myeloid leukemia were reported since the first analysis published in 2012, 2 in patients originally randomized to ruxolitinib and 2 in the placebo arm, for a total of 8 cases since the study began. The rate of leukemic transformation per person-year of ruxolitinib exposure was 0.0121 per person-year and 0.0233 per person-year in patients originally randomized to ruxolitinib or placebo, respectively.

Although identification of a drug, producing long-term remission (like imatinib in chronic myeloid leukemia) is the ultimate goal, discovery likely will be complicated by the complexity of molecular processes occurring in patients with these other MPNs and the fact that JAK2 V617F alone does not appear to be a unique or absolutely necessary event in many patients with these diseases. The role of the JAK2 V617F variant in selecting or monitoring patients for new treatments or residual neoplasia remains undefined.

Section Summary: Clinically Useful

Evidence for the clinical utility of JAK2 testing includes meta-analyses, retrospective studies, and RCTs. Evidence for JAK2 testing for phenotyping and monitoring provides conflicting results. However, the presence of JAK2 V617F or JAK2 exon 12 variants is considered a major criterion for the diagnosis of PV, ET, and PMF. JAK2 V617F and JAK2 exon 12 testing allow secondary or reactive erythrocytosis or thrombocytosis to be differentiated from PV, ET, and PMF.

MPL Testing for a Suspected Myeloproliferative Neoplasm

Clinical Context and Test Purpose

The purpose of MPL testing of individuals with a suspected MPN is to establish a molecular genetic diagnosis of MPN to inform management decisions.

The question addressed in this policy is: In individuals with a suspected MPN, does the use of MPL testing result in improvement in the net health outcome?

The following PICOs were used to select literature to inform this policy.

Patients

The relevant population of interest includes individuals with a suspected MPN.

Patients with suspected MPN are actively managed by hematologists and oncologists.

Interventions

The test being considered is genetic testing for MPL.

Comparators

The following practice is currently being used to make decisions about treating individuals with a suspected MPN: standard clinical management without genetic testing.

Outcomes

The potential beneficial outcomes of primary interest include establishing a molecular genetic diagnosis of ET or PMF to inform management decisions when test results are positive.

The time frame for outcomes measures varies from several months for the improvement of symptoms to long-term survival as a result of disease-related complications.

Technically Reliable

Assessment of technical reliability focuses on specific tests and operators and requires a review of unpublished and often proprietary information. Review of specific tests, operators, and unpublished data are outside the scope of this policy and alternative sources exist. This policy focuses on the clinical validity and clinical utility.

Clinically Valid

A test must detect the presence or absence of a condition, the risk of developing a condition in the future, or treatment response (beneficial or adverse).

Mejia-Ochoa et al (2019) conducted a systematic review and meta-analysis of the frequency of JAK2, CALR, and MPL in Ph-negative chronic MPNs.^34, Across 14 studies, the frequency of the MPL variant ranged from 0% in PV, from 0.9% to 12.5% in ET, and from 0% to 17.1% in PMF. The studies were heterogeneous with regard to the diagnostic techniques used and their results.

The WHO (2016) criteria specifically cited testing MPL exon 10 variants in patients with ET and PMF. The criteria included testing for MPL exon 10 variants in patients with ET and PMF.^6,

Section Summary: Clinically Valid

Evidence of the clinical validity MPL exon 10 variants includes case series. The frequency of the MPL variant ranged from 0% in PV, from 0.9% to 12.5% in ET, and from 0% to 17.1% in PMF. In ET and PMF patients, the WHO(2016) incorporated MPL exon 10 variants as a major criterion for the diagnosis of ET and PMF.

Clinically Useful

A test is clinically useful if the use of the results informs management decisions that improve the net health outcome of care. The net health outcome can be improved if patients receive correct therapy, or more effective therapy, or avoid unnecessary therapy, or avoid unnecessary testing.

Direct Evidence

Direct evidence of clinical utility is provided by studies that have compared health outcomes for patients managed with and without the test. Because these are intervention studies, the preferred evidence would be from RCTs.

Testing for MPL exon 10 variants has potential clinical utility in several different clinical scenarios:

1. Diagnosis of patients with clinical, laboratory, or pathologic findings suggesting classic ET or PMF;
2. Phenotyping of disease subtypes in patients with ET and PMF to establish disease prognosis.

Section Summary: Clinically Useful

Direct evidence for the clinical utility of MPL testing is lacking. While MPL exon 10 testing has potential utility in diagnosing ET and PMF using the WHO(2016) major criteria for MPNs and excluding reactive or secondary causes of thrombocytosis, there is no change in management that would be expected to improve the net health outcome. Thus, the clinical utility has not been established. Given that genetic testing for CALR is included in the WHO (2016) major criteria and the National Comprehensive Cancer Network guidelines (2019) for myeloproliferative neoplasms, MPL testing may be consistent with clinical practice in the diagnosis of patients with clinical, laboratory, or pathological findings suggesting ET and PMF.

CALR Testing for a Suspected Myeloproliferative Neoplasm

Clinical Context and Test Purpose

The purpose of CALR testing of individuals with a suspected MPN is to establish a molecular genetic diagnosis of MPN to inform management decisions.

The question addressed in this policy is: In individuals with a suspected MPN, does the use of CALR testing result in improvement in health outcomes?

The following PICOs were used to select literature to inform this policy.

Patients

The relevant population of interest includes individuals with a suspected MPN.

Patients with suspected MPN are actively managed by hematologists and oncologists.

Interventions

The test being considered is genetic testing for CALR.

Comparators

The following practice is currently being used to make decisions about individuals with a suspected MPN: standard clinical management without genetic testing.

Outcomes

The potential beneficial outcomes of primary interest include establishing a molecular genetic diagnosis of ET or PMF to inform management decision when test results are positive.

The time frame for outcomes measures varies from several months for the improvement of symptoms to long-term survival as a result of disease-related complications.

Technically Reliable

Assessment of technical reliability focuses on specific tests and operators and requires a review of unpublished and often proprietary information. Review of specific tests, operators, and unpublished data are outside the scope of this policy and alternative sources exist. This policy focuses on the clinical validity and clinical utility.

Clinically Valid

A test must detect the presence or absence of a condition, the risk of developing a condition in the future, or treatment response (beneficial or adverse).

Mejia-Ochoa et al (2019) conducted a systematic review and meta-analysis of the frequency of JAK2, CALR, and MPL in Ph-negative chronic MPNs.^34, Thirteen studies reported the frequency of the CALR variant in PV, ET, and PMF. The studies were heterogeneous with regard to the diagnostic techniques used and their results. The frequency of the CALR variant was 0% in patients with PV, 12.6% to 50.0% in ET, and 10% to 100% in PMF.

Section Summary: Clinically Valid

Evidence of the clinical validity CALR variants includes retrospective studies, case series, and a systematic review of these studies. The frequency of the CALR variant was 0% in patients with PV, 12.6% to 50.0% in ET, and 10% to 100% in PMF.

Clinically Useful

A test is clinically useful if the use of the results informs management decisions that improve the net health outcome of care. The net health outcome can be improved if patients receive correct therapy, or more effective therapy, or avoid unnecessary therapy, or avoid unnecessary testing.

Direct evidence of clinical utility is provided by studies that have compared health outcomes for patients managed with and without the test. Because these are intervention studies, the preferred evidence would be from RCTs.

Testing for CALR exon 9 variants has potential clinical utility in several different clinical scenarios:

1. Diagnosis of patients with clinical, laboratory, or pathologic findings suggesting classic ET or PMF;
2. Phenotyping of disease subtypes in patients with ET and PMF to establish disease prognosis.

The goals of treatment and management for ET are to alleviate symptoms and minimize complications of the disease such as thrombotic events and bleeding, though establishing the diagnosis does not lead to preventive management. For PMF, hematopoietic cell transplantation is the only treatment with curative potential while most other treatment options focus on alleviation of symptoms.

Section Summary: Clinically Useful

Direct evidence for the clinical utility of CALR testing is lacking. While CALR exon 9 testing has potential clinical utility in diagnosing ET and PMF using the WHO(2016) major criteria for MPNs and excluding reactive or secondary causes of thrombocytosis, there is no change in management that would be expected to improve net health outcome. Thus, the clinical utility has not been established.

Summary of Evidence

For individuals with a suspected MPN who receive genetic testing for JAK2, the evidence includes case series, retrospective studies, meta-analyses, and RCTs. The relevant outcomes include OS, disease-specific survival, test accuracy and validity, and resource utilization. For patients with suspected Ph-negative MPN, JAK2 variants are found in nearly 100% of those with PV, 60% to 65% of those withET, and 60% to 65% of those with PMF. In individuals with suspected MPN, a positive genetic test for JAK2 satisfies a major criterion for the World Health Organization (2016) classification for Ph-negative MPNs and eliminates secondary or reactive causes of erythrocytosis and thrombocythemia from the differential diagnosis. The presence of a documented JAK2 variant may aid in the selection of ruxolitinib, a JAK2 inhibitor; ruxolitinib, however, is classified as second-line therapy. The evidence is sufficient to determine that the technology results in a meaningful improvement in the net health outcome.

For individuals with a suspected MPN who receive genetic testing for MPL, the evidence includes case series and retrospective studies. The relevant outcomes include OS, disease-specific survival, test accuracy and validity, and resource utilization. For patients with suspected Ph-negative MPN, MPL variants are found in approximately 5% of those with ET and PMF. In individuals with suspected MPN, a positive genetic test for MPL satisfies a major criterion for the World Health Organization (2016)classification for ET and PMF and eliminates secondary or reactive causes of thrombocythemia from the differential diagnosis. The goal of ET treatment is to alleviate symptoms and minimize thrombotic events and bleeding irrespective of MPL variant status. For PMF, hematopoietic cell transplantation is the only treatment with curative potential while most other treatment options focus on symptom alleviation. However, in both ET and PMF, establishing the diagnosis through MPL genetic testing does not in and of itself result in changes in management that would be expected to improve the net health outcome. Thus, the clinical utility has not been established. The evidence is insufficient to determine that the technology results in a meaningful improvement in the net health outcome.

For individuals with a suspected MPN who receive genetic testing for CALR, the evidence includes case series and retrospective studies. The relevant outcomes include OS, disease-specific survival, test accuracy and validity, and resource utilization. For patients with suspected Ph-negative MPN, CALR variants are found in approximately 20% to 25% of those with ET and PMF. For individuals with suspected MPN, a positive genetic test for CALR satisfies a major criterion for the World Health Organization classification for ET and PMF and eliminates secondary or reactive causes of thrombocythemia from the differential diagnosis. The goal of ET treatment is to alleviate symptoms and minimize thrombotic events and bleeding irrespective of CALR variant status. For PMF, hematopoietic cell transplantation is the only treatment with curative potential while most other treatment options focus on symptom alleviation. However, in both ET and PMF, establishing the diagnosis through CALR genetic testing does not result in changes in management that would be expected to improve the net health outcome. Thus, the clinical utility has not been established. The evidence is insufficient to determine that the technology results in a meaningful improvement in the net health outcome

SUPPLEMENTAL INFORMATION

Practice Guidelines and Position Statements

World Health Organization (2016) major criteria for myeloproliferative neoplasms are as follows^6,:

Polycythemia vera: "Presence of JAK2 V617F or other functionally similar mutation such as JAK2 exon 12 mutation"

Essential thrombocythemia: "Demonstration of JAK2 V617F or other clonal markers, or in the absence of a clonal marker, no evidence for reactive thrombocytosis"

Primary myelofibrosis: "Demonstration of JAK2 V617F or other clonal markers (e.g., MPL W515K/L), or, in the absence of a clonal marker, no evidence of bone marrow fibrosis [due to underlying inflammatory or other neoplastic disease]."

National Comprehensive Cancer Network

The National Comprehensive Cancer Network published guidelines (v.2.2018) on the workup, diagnosis, and treatment of suspected myeloproliferative neoplasms. For patients with suspicion of myeloproliferative neoplasms, the guidelines recommend "molecular testing (blood) for JAK2 V617F mutation; if negative, test for CALR and MPL mutations (for patients with ET and MF) and JAK2 Exon 12 mutations (for patients with PV)."

U.S. Preventive Services Task Force Recommendations

Not applicable.

Ongoing and Unpublished Clinical Trials

A search of ClinicalTrials.gov in July 2019 did not identify any ongoing or unpublished trials that would likely influence this review..]
________________________________________________________________________________________

Horizon BCBSNJ Medical Policy Development Process:

This Horizon BCBSNJ Medical Policy (the “Medical Policy”) has been developed by Horizon BCBSNJ’s Medical Policy Committee (the “Committee”) consistent with generally accepted standards of medical practice, and reflects Horizon BCBSNJ’s view of the subject health care services, supplies or procedures, and in what circumstances they are deemed to be medically necessary or experimental/ investigational in nature. This Medical Policy also considers whether and to what degree the subject health care services, supplies or procedures are clinically appropriate, in terms of type, frequency, extent, site and duration and if they are considered effective for the illnesses, injuries or diseases discussed. Where relevant, this Medical Policy considers whether the subject health care services, supplies or procedures are being requested primarily for the convenience of the covered person or the health care provider. It may also consider whether the services, supplies or procedures are more costly than an alternative service or sequence of services, supplies or procedures that are at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of the relevant illness, injury or disease. In reaching its conclusion regarding what it considers to be the generally accepted standards of medical practice, the Committee reviews and considers the following: all credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, physician and health care provider specialty society recommendations, the views of physicians and health care providers practicing in relevant clinical areas (including, but not limited to, the prevailing opinion within the appropriate specialty) and any other relevant factor as determined by applicable State and Federal laws and regulations.

___________________________________________________________________________________________________________________________

Index:
JAK2, MPL, and CALR Testing for Myeloproliferative Neoplasms
JAK2 and MPL Mutation Analysis in Myeloproliferative Neoplasms
Tyrosine Kinase Mutations in Myeloproliferative Neoplasms
JAK2 (Janus Kinase 2) Gene Mutation Testing
Janus Kinase 2 (JAK2) Gene Mutation Testing
MPL (Myeloproliferative Leukemia Virus Oncogene) Testing
Myeloproliferative Leukemia Virus Oncogene (MPL) Testing
CALR Testing for Myeloproliferative Neoplasms

References:
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21. Sidon P, El Housni H, Dessars B, et al. The JAK2V617F mutation is detectable at very low level in peripheral blood of healthy donors. Leukemia. Sep 2006;20(9):1622. PMID 16775613.

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28. Rambaldi A, Dellacasa CM, Finazzi G, et al. A pilot study of the histone-deacetylase inhibitor givinostat in patients with JAK2V617F positive chronic myeloproliferative neoplasms. Br J Haematol. Aug 2010;150(4):446- 455. PMID 20560970.

29. Santos FP, Kantarjian HM, Jain N, et al. Phase 2 study of CEP-701, an orally available JAK2 inhibitor, in patients with primary or post-polycythemia vera/essential thrombocythemia myelofibrosis. Blood. Feb 11 2010;115(6):1131-1136. PMID 20008298.

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32. Harrison C, Kiladjian JJ, Al-Ali HK, et al. JAK inhibition with ruxolitinib versus best available therapy for myelofibrosis. N Engl J Med. Mar 1 2012;366(9):787-798. PMID 22375970.

33. Verstovsek S, Mesa RA, Gotlib J, et al. Efficacy, safety, and survival with ruxolitinib in patients with myelofibrosis: results of a median 3-year follow-up of COMFORT-I. Haematologica. Apr 2015;100(4):479-488. PMID 25616577.

34. Mejía-Ochoa, MM, Acevedo Toro, PP, Cardona-Arias, JJ. Systematization of analytical studies of polycythemia vera, essential thrombocythemia and primary myelofibrosis, and a meta-analysis of the frequency of JAK2, CALR and MPL mutations: 2000-2018. BMC Cancer, 2019 Jun 19;19(1). PMID 31208359.

Codes:
(The list of codes is not intended to be all-inclusive and is included below for informational purposes only. Inclusion or exclusion of a procedure, diagnosis, drug or device code(s) does not constitute or imply authorization, certification, approval, offer of coverage or guarantee of payment.)

CPT*

81219
81270
81402
81403
0017U