The following Coverage Policy applies to health benefit plans administered by Cigna Companies.

Certain Cigna Companies and/or lines of business only provide utilization review services to clients and do not make coverage determinations. References to standard benefit plan language and coverage determinations do not apply to those clients. Coverage Policies are intended to provide guidance in interpreting certain standard benefit plans administered by Cigna Companies. Please note, the terms of a customer’s particular benefit plan document [Group Service Agreement, Evidence of Coverage, Certificate of Coverage, Summary Plan Description (SPD) or similar plan document] may differ significantly from the standard benefit plans upon which these Coverage Policies are based. For example, a customer’s benefit plan document may contain a specific exclusion related to a topic addressed in a Coverage Policy. In the event of a conflict, a customer’s benefit plan document always supersedes the information in the Coverage Policies. In the absence of a controlling federal or state coverage mandate, benefits are ultimately determined by the terms of the applicable benefit plan document.

Coverage determinations in each specific instance require consideration of 1) the terms of the applicable benefit plan document in effect on the date of service; 2) any applicable laws/regulations; 3) any relevant collateral source materials including Coverage Policies and; 4) the specific facts of the particular situation. Each coverage request should be reviewed on its own merits. Medical directors are expected to exercise clinical judgment where appropriate and have discretion in making individual coverage determinations. Where coverage for care or services does not depend on specific circumstances, reimbursement will only be provided if a requested service(s) is submitted in accordance with the relevant criteria outlined in the applicable Coverage Policy, including covered diagnosis and/or procedure code(s). Reimbursement is not allowed for services when billed for conditions or diagnoses that are not covered under this Coverage Policy (see "Coding Information" below). When billing, providers must use the most appropriate codes as of the effective date of the submission. Claims submitted for services that are not accompanied by covered code(s) under the applicable Coverage Policy

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will be denied as not covered. Coverage Policies relate exclusively to the administration of health benefit plans. Coverage Policies are not recommendations for treatment and should never be used as treatment guidelines. In certain markets, delegated vendor guidelines may be used to support medical necessity and other coverage determinations.

This Coverage Policy addresses the indications for flow cytometry.

Flow cytometry is a laboratory test used to separate, classify and count cells. It is clinically useful in the diagnosis and/or evaluation of hematopoietic cancers, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), primary immunodeficiency disorders, molar pregnancies, paroxysmal hemoglobinuria and monitoring after transplantation.

Coverage Policy

Flow cytometry is considered medically necessary for the evaluation of any of the following:

• Hematopoietic/hematologic cancers
• Immunodeficiency disorders, including human immunodeficiency virus (HIV) and acquired immunodeficiency virus syndrome (AIDS)
• Paroxysmal nocturnal hemoglobinuria
• Gestational trophoblastic disease
• Transplantation

Flow cytometry for any other indication is not covered or reimbursable.

General Background

A flow cytometer separates, classifies and counts cells that are suspended in a moving fluid medium as they pass through a beam of light.

This method may be used to evaluate cells from blood, bone marrow, body fluids such as cerebrospinal fluid (CSF), or tumor tissue. Unlike other biochemical techniques, flow cytometry makes these multiparametric measurements on single cells as opposed to population measurements (National Institutes of Health, 2018). Flow cytometry is an established laboratory test that measures cell surface antigen expression, also known as immunophenotyping. It is clinically useful for the diagnosis and prognosis of hematopoietic cancers, including lymphomas and leukemia, plasma cell neoplasms, myelodysplastic syndromes, myeloproliferative neoplasms, and certain anemias (Borowitz, 2014; Craig and Foon, 2008). Flow cytometry is commonly used to detect the presence of minimal residual disease and antigens used as therapeutic drug targets for cancer therapy. Professional society consensus support is noted in the National Comprehensive Cancer Network (NCCN®) Biomarker Compendium (2020) for certain cancer types as noted below in the Professional Societies/Organizations section.

Other uses of flow cytometry include monitoring lymphocyte populations, (e.g., T-cells, natural killer [NK] cells) in an individual with a primary immunodeficiency disorder or human immunodeficiency virus/acquired immunodeficiency syndrome [HIV/AIDs]) by tracking the number and ratio of antigen-specific T cells (CD4, CD8). CD4 T-cell counting in peripheral blood of Medical Coverage Policy: 0538 HIV1 patients using flow cytometry is considered routine practice in clinical laboratories as an important tool in the management of HIV disease. Specifically, CD4 counts are used as a measure of the degree of immune deficiency, eligibility of HIV1 patients for antiretroviral treatment and to monitor immune restoration in an individual receiving antiretroviral therapy. CD4 T-cell counting is a valuable tool for directing treatment against opportunistic infections (Kestens and Mandy, 2017).

It is also clinically useful to detect chimerism and rejection following transplantation, and to monitor the toxicity or effectiveness of immunosuppressive therapy (Antin, et al., 2001). Flow cytometry is considered the most sensitive and informative assay available for diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). It is considered the gold standard for identifying peripheral blood cells that are missing glycosylphosphatidylinositol (GPI)–anchored proteins (National Organization for Rare Disorders [NORD], 2020; Parker, 2016; Borowitz, et al., 2010).

Flow cytometry is considered a standard laboratory method to assess deoxyribonucleic acid (DNA) ploidy in gestational trophoblastic disease, including molar pregnancies; however, it is also proposed as a method to measure nuclear deoxyribonucleic acid (DNA) content (i.e., ploidy) and cell proliferation activity (i.e., S-phase fraction) for cancer in solid tumors. Correlation of ploidy and DNA activity with proliferation and aggressiveness of disease is primarily limited to retrospective, correlational studies. There are limited data in the published scientific literature to demonstrate improved health outcomes for this indication. Likewise, there is a lack of professional society consensus by way of published guidelines and recommendations for this purpose. The role of flow cytometry, including to determine ploidy and cell proliferation activity, has not been established for cancer in solid tumors. Use of multiparametric flow cytometry in solid tumors is of ongoing research interest.

Literature Review

Borowitz (2014) notes the literature is confusing and contradictory regarding the use of flow cytometry to determine DNA ploidy and that the early promise of this measurement as an important diagnostic and prognostic marker in cancer has not been realized. Although some studies have demonstrated prognostic significance to measurements of ploidy, and especially S- phase fraction, in a number of tumors—most specifically bladder, prostate, and breast cancer— many studies conflict, and as a result, this technology has not been widely embraced in clinical oncology. DNA flow cytometry has largely been replaced by molecular prognostic markers. It is unlikely that these techniques will be adopted in routine clinical practice.

Ye et al. (2019) compared the ability of flow cytometry (FCM) and cytomorphology (CM) in detecting neuroblastoma cells in 21 patients with neuroblastoma metastasis. Bone marrow and effusion specimens were analyzed by flow cytometry and cytomorphology. Cytomorphology detected three effusions not detected by flow cytometry. There was no significant difference between FCM and CM in the detection of NB cells in effusions (p = 0.344). Further studies are needed to demonstrate improved health benefit for the use of flow cytometry compared to conventional cytomorphology techniques.

Ludovini et al. (2008) reported on a study evaluating the relationship between a panel of biological markers (p53, Bcl-2, HER-2, Ki67, DNA ploidy and S-phase fraction) and clinical-pathological parameters and its impact on outcomes in non-small cell lung cancer (NSCLC). Tumor tissue specimens were collected from 136 consecutive patients with NSCLC following surgical resection. An immunocytochemical technique and flow cytometric DNA analysis were used to evaluate p53, Bcl-2, HER-2 and Ki67. Positivity of p53, Bcl-2, HER-2 and Ki67 was detected in 51.4%, 27.9%, 25.0% and 55.8% of the samples, respectively; 82.9% of the cases revealed aneuploid DNA histograms and 56.7% presented an S-phase fraction of more than 12%. At univariate analysis, high Ki67 proved to be the only marker associated with disease-free survival (p = 0.047). After adjusting for stage, none of the examined immunocytochemical markers emerged
as an independent factor for disease-free and overall survival; only pathological stage was identified as an independent prognostic factor for disease-free survival (p = 0.0001) and overall survival (p = 0.0001). The authors concluded the findings do not support a relevant prognostic role of immunocytochemical markers in NSCLC.

Dayal et al. (2013) published results of a retrospective correlational study reporting on the application of multiparameter flow cytometry and to examine the clinical and biomarker associations in 201 formalin-fixed, paraffin-embedded FFPE previously banked breast cancer specimens. Tumors were grouped into four categories based on the DNA index of the tumor cell population. Univariate statistical analysis demonstrated significant association with tumor category and prognosis in three of four tumor groups; however, an independent association between tumor DNA content and overall survival was not confirmed by multivariate analysis. Further study is indicated before flow cytometry can be considered a standard clinical practice for the detection of breast cancer ploidy or DNA index.

Wolfson et al. (2008) reported results of a retrospective study looking for possible associations between measurements of DNA index (DI), S-phase fraction (SPF) and tumor heterogeneity (TH) using flow cytometry in 57 patients with invasive cervical carcinoma.

Patients had International Federation of Obstetrics and Gynecology Stages IB2 through IVB cervical carcinomas treated with definitive radiotherapy with or without concurrent chemotherapy. With a median follow-up of 3.7 years, there were no statistically significant associations by univariate analysis for DI, SPF, or TH and patient outcome or survival. The authors note additional studies are indicated to identify tumor biomarkers that could predict patients at risk for disseminated disease.

Davis et al. (2007) published international consensus recommendations regarding the use of flow cytometry for hematologic neoplasia. Uses recommended are cytopenias, elevated leukocyte count, identification of blasts in the marrow or peripheral blood, plasmacytosis or monoclonal gammopathy, tissue-based lymphoid neoplasia, lymph adenopathy, staging disease to document the extent of involvement, detecting potential therapeutic targets, assessment of response to therapy (e.g., minimal residual disease), documentation of progression or relapse, diagnosis of related disease (e.g., treatment-related or coincidental), documentation of disease acceleration, and prognostication.

Professional Societies/Organizations

• American Society for Clinical Pathology: In a 2018 Choosing Wisely statement, the American Society for Clinical Pathology stated, "Do not perform peripheral blood flow cytometry to screen for hematological malignancy in the settings of mature neutrophilia, basophilia, erythrocytosis, thrombocytosis, isolated anemia, or isolated thrombocytopenia."

National Cancer Institute ([NCI], 2018):

• Adult soft tissue sarcoma: The NCI notes flow cytometry is one of several techniques that may allow identification of particular subtypes within the major histologic categories
• Transitional cell cancer of the renal pelvis and ureter:
• Regarding prognosis, DNA ploidy has not added significant prognostic information beyond that provided by stage and grade.
• In metastatic disease, flow cytometry analysis identifies low-stage, low-grade tumors at high risk of recurrence by virtue of their aneuploidy histograms.
• Neuroblastoma: Regarding prognosis, low-risk tumors are hyperdiploid when examined by flow cytometry. In contrast, in high-risk neuroblastoma, tumors are near diploid or near tetraploid by flow cytometric measurement.
• Ovarian epithelial cancer: Ploidy may identify high risk in analysis of stage 1 and 2a tumors

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• Prostate cancer: DNA ploidy is associated with outcome

The National Comprehensive Cancer Network (NCCN®) Biomarkers Compendium® (2020): The Compendium notes that flow cytometry may be used to assess the following hematologic lymphoid cancers:

• Acute lymphoblastic leukemia
• Chronic myeloid leukemia
• Lymphomas
• Hairy cell leukemia
• Myeloproliferative neoplasms
• Myelodysplastic disorders
• Multiple myeloma
• Systemic mastocytosis
• Waldenstrom’s macroglobinemia

Flow cytometry is not mentioned in the Compendium as a laboratory method used for the diagnosis or management of solid tumors, including any of the following: bladder, brain, breast, colon, endometrium, gastric, kidney, lung, neuroblastoma, ovary, prostate or rectum.

International Bone Marrow Transplant Registry (IBMTR) and the American Society of Blood and Marrow Transplantation (ASBMT):

Antin et al. (2001) published recommendations from a workshop at the 2001 Tandem Meetings of the IBMTR/ASBMT concerning the establishment of complete- and mixed-donor chimerism following allogeneic lymphohematopoietic transplantation and the role of flow cytometry in determining chimerisms of neutrophil, monocyte, and lymphocyte fractions.

Use Outside of the US: N/A