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Tumor Chemosensitivity and Chemoresistance Assays

» Summary» Procedure Codes
» Description» Selected References
» Prior Approval» Policy History
» Policy

Medical Policy: 02.04.47 
Original Effective Date: August 2014 
Reviewed: July 2015 
Revised: July 2015 

Benefit Application
Benefit determinations are based on the applicable contract language in effect at the time the services were rendered. Exclusions, limitations or exceptions may apply. Benefits may vary based on contract, and individual member benefits must be verified. Wellmark determines medical necessity only if the benefit exists and no contract exclusions are applicable. This medical policy may not apply to FEP. Benefits are determined by the Federal Employee Program.

This Medical Policy document describes the status of medical technology at the time the document was developed. Since that time, new technology may have emerged or new medical literature may have been published. This Medical Policy will be reviewed regularly and be updated as scientific and medical literature becomes available.


Chemosensitivity assay testing is intended to predict the sensitivity of various tumors to chemotherapeutic agents to assist with the selection of chemotherapy drugs with the intent of identifying more effective protocols which would then translate into improved clinical survival. Chemoresistance assay testing is intended to identify chemotherapeutic agents to which a patient’s tumor is resistant, and therefore assist in identifying those specific chemotherapeutic dugs that are non-responsive to a specific tumor and not recommended as part of the treatment protocol.


The various assays differ in their processing and in the technique used to measure sensitivity or resistance. However, there are 4 basic steps common to all:

  • Isolation of cells
  • Incubation of cells with drugs
  • Assessment of cell survival
  • Interpretation of the result 

A tumors response to the drug is classified as sensitive or resistant, although sometimes tumors are described as intermediate. Drugs identified as sensitive are thought to be potentially effective chemotherapies, while drugs identified as resistant are thought to be potentially ineffective chemotherapies. 


All assays use characteristics of cell physiology to distinguish between viable and non-viable cells to quantify cell kill following exposure to a drug of interest. With few exceptions, drug doses used in the assays are highly variable depending on the tumor type and drug class, but all assays require drug exposure ranging from several-fold below physiological relevance to several-fold above physiological relevance. Although a variety of assays exist to examine chemosensitivity and chemoresistance, only a few are commercially available. Available assays are outlined as follows:


Methods using differential staining/dye exclusion:

  • The Differential Staining Cytotoxicity assay: This assay relies on dye exclusion of live cells after mechanical disaggregation of cells from surgical or biopsy specimens by centrifugation. Cells are then established in culture and treated with the drugs of interest at 3 dose levels; the middle dose is that which could be achieved in therapy; 10-fold lower than the physiologically relevant dose; and, 10-fold higher. Exposure time ranges from 4 to 6 days; then, cells are restained with fast green dye and counterstained with hematoxylin and eosin (H&E). The fast green dye it taken up by dead cells, and H&E can then differentiate tumors cells from normal cells. The intact cell membrane of a live cell precludes staining with the green dye. Drug sensitivity is measured by the ratio of live cells in the treated samples to the number of live cells in the untreated controls.
  • The EVA-PCD® functional profile (Ex Vivo Analysis of Programmed Cell Death) (available from Rationale Therapeutics). This functional profile is a laboratory analysis that exposes patients living tumor cells to chemotherapy drugs/combinations and single transduction inhibitors (targeted agents). Drug induced cell death (apoptotic & non-apoptotic) is examined by morphology, cytochemistry, staining characteristics and cellular metabolism. Living cells versus dead cells show which drugs kill the cancer cells (sensitive) and which one do not (resistant). Each patient’s dose response analysis of drug sensitivity, resistance and formal synergy is then compared with Rational Therapeutics’ extensive database and an individualized comprehensive report is generated. Results take 7-10 days from the receipt of the specimen in the laboratory.
    • Patient drug panels are disease specific and based on previous treatment history. A typical panel consists of 8 to 16 drugs/combinations. Quantity of the drugs analyzed is totally dependent upon the quantity/quality of tumor received in the laboratory.
    •  At Rationale Therapeutics they do not grow, subculture or propogate cells in the lab. Tumor cells are kept in clusters (microspheroids) that mimic the body’s environment. By examining cells in their native state, they take a snapshot of their behavior in response to drugs. The microspheroids reflect the complex elements of the body’s cellular environment.
    • After drug exposure is completed, a mixture of Nigrosin B & Fast green dye with glutaraldehyde-fixed avian erythrocytes is added to the cellular suspensions. The samples are then agitated and cytospin-centrifuged and, after air drying, are counterstained with H&E. The end point of interest for this assay is cell death, as assessed by observing the number of cells differentially stained due to changes in cellular membrane integrity. 
  • The fluorometric microculture cytotoxicity assay is another cell viability assay that relies on the measurement of fluorescence generated from cellular hydrolysis of fluorescein diacetate to fluorescein in viable cells. Cells from tumor specimens are incubated with cytotoxic drugs; drug resistance is associated with higher levels of fluorescence.


Methods using incorporation of radioactive precursors by macromolecules in viable cells: 

  • Tritiated thymine incorporation measures uptake of tritiated thymidine by DNA of viable cells. Using proteases and DNAse to disaggregate the tissue, samples are seeded into single cell suspension cultures on soft agar. They are then treated with the drug(s) of interest for 4 days. After 3 days, tritiated thymidine is added. After 24 hours of additional incubation, cells are lysed, and radioactivity is quantified and compared with a blank control consisting of cells that were treated with sodium azide. Only cells that are viable and proliferating will take up the radioactive thymidine. Therefore, there is an inverse relationship between update of radioactivity and sensitivity of the cells to the agent(s) of interest.
  • The Extreme Drug Resistance assay (EDR Assays ®) (commercially available at Exiqon Diagnostics, Tustin, CA). These tests are available for all major cancers and make it possible for physicians to decide whether a patient is resistant to one or more approved chemotherapies for specific cancers.
    • This assay is similar to the thymidine incorporation assay, using metabolic incorporation of tritiated thymidine to measure cell viability; however, single cell suspensions are not required, so the assay is simpler to perform. Small tissue samples are incubated with the drug(s) of interest for 5 days at doses ranging from 5-fold below to 80-fold above concentrations that would reflect physiologic relevance. Subsequently, tritiated thymidine is added to the culture, and uptake is quantified after various incubation times. Only live (resistant) cells will incorporate the compound. Therefore, the level of tritiated thymidine incorporation is directly related to chemoresistance. The interpretation of the results is unique in that resinstance to the drugs is evaluated, as opposed to evaluation of responsiveness. Tumors are considered to be highly resistant when thymidine incorporation is at least 1 standard deviation above reference samples.  


Methods to quantify cell viability by colormetric assay:

  • The Histoculture Drug Response Assay (HDRA) (AntiCancer Inc., San Diego, CA). The HDRA determines both drug sensitivity and resistance. This assay evaluates cell growth after chemotherapy treatment based on colorimetric assay that relies on mitochondrial dehydrogenases in living cells. Drug sensitivity is evaluated by quantification of cell growth in a three dimensional culture (collagen matrix). There is an inverse relationship between the drug sensitivity of the tumor and cell growth. Concentrations of drug and incubation times are not standardized and vary depending on drug combination and tumor types.


Methods using incorporation of chemoluminescent percursors by macromolecules in viable cells:

  • The Adenosine Thriphosphate (ATP) Bioluminescence assay, relies on measurement of ATP to quantify the number of viable cells in a culture. Single cells or small aggregates are cultured, and then exposed to drugs. Following incubation with drug, the cells are lysed and the cytoplasmic components are solubilized under conditions that will not allow enzymatic metabolism of ATP. Luciferin and firefly luciferase are added to cell lysis product. This catalyzes the conversion of APT to adenosine di-and monophosphate, and light is emitted proportionally to metabolic activity. This is quantified with a luminometer. From the measurement of light, the number of cells can be calculated. A decrease in ATP indicates drug sensitivity, whereas no loss of ATP suggests that the tumor is resistant to the agent of interest.

  • ChemoFx ® – (Precision Therapeutics, Pittsuburg, PA). This assay relies on quantifying adenosine triphosphate (ATP) based on chemoluminescence. Cells must be grown in a monolayer rather than a three dimensional matrix. ChemoFx was designed to show chemotherapy resistance and sensitivity over a broad range of agents and gynecologic tumor types, including ovarian, endometrial and cervical cancers. As such, ChemoFx it utilized to help guide physician’s treatment decisions to assist in determining which chemotherapies are least likely to work and which are most likely to work for an individual patient. 


Methods using differential optical density:

  • Microculture Kinetic (MiCK) Assay – (DiaTech Oncology, Franklin, TN). Diatech Oncology utilizes a proprietary and patented technology called CorrectChemo, also known as the Microculture Kinetic (MiCK) assay, licensed from Vanderbilt University. This assay relies on measures of programed cell death. In the assay, tumor cells are exposed to multiple concentrations of drugs and cultured. The optical density of the cells is measured over time, to create a density-by-time curve. A sudden increase in optical density is associated with cell apoptosis; the extent of the drug induced apoptosis is a measures of the cell’s sensitivity to that agent.
    • Measures apoptotic cancer cell death to predict chemotherapy treatment outcomes within 72 hours.
    • The assay has been used in more than 50 different tumor types.
    • Based on the result, DiaTech Oncology provides the treating oncologist with a clinically relevant drug-induced apoptosis profile of tumor cells of an individual cancer patient.


Assay guided chemotherapy is proposed as an alternative to empiric therapy (regimens). Empiric therapy (regimens) refers to selection of chemotherapy based on critical evaluation of outcome evidence from well-designed clinical trials. Empiric therapy (regimens) is selected based on specific patient indications determined by tumor type, stage, prognostic factors, and treatment history.


There are only a few comparative studies that evaluate use of chemosensitivity assay to select chemotherapy versus standard of care, and these studies do not report significant differences in outcomes between groups. A larger number of studies have used correlational designs that evaluate the association between assay results and already known patient outcomes. These studies do not evaluate whether these assays lead to changes in management and whether any changes in management lead to improved outcomes. As a result, the clinical utility of chemoresistance and chemosensitivity assays has not been determined, and the data is insufficient to determine whether the use of this testing to select chemotherapy regimens for individual patients will improve outcomes. Therefore, this testing is considered investigational.


Practice Guidelines and Position Statements


National Comprehensive Cancer Network (NCCN)
NCCN Guidelines Version 2.2015 Ovarian, Fallopian and Primary Peritoneal Cancer

Chemotherapy/resistance assays and/or other biomarker assays are being used in some NCCN Member Institutions to aid in selecting chemotherapy in situations where there are multiple equivalent chemotherapy options available; however, the current level of evidence (category 3) is not sufficient to supplant standard of care chemotherapy. Thus, the NCCN Panel felt that in vitro chemosensitivity testing to choose a chemotherapy regimen for recurrent disease situations should not be recommended (category 3), owing to the lack of demonstrable efficacy for such an approach. The ASCO also does not recommend use of chemotherapy sensitivity and resistance assays, unless in a clinical trial setting.


American Society of Clinical Oncology (ASCO)
The American Society of Clinical Oncology (ASCO) Clinical Practice Guideline Update on the Use of Chemotherapy Sensitivity and Resistance Assays, 2011: The use of chemotherapy sensitivity and resistance assays to select chemotherapeutic agents for individual patients is not recommended outside of the clinical trial setting. Oncologists should make chemotherapy treatment recommendations on the basis of published reports of clinical trials and a patient’s health status and treatment preferences. Because in in-vitro analytic strategy has potential importance, participation in clinical trials evaluating these technologies remains a priority. 


Regulatory Status
Commercially available chemosensitivity and chemoresistance assays are laboratory developed tests for which approval from the U.S. Food and Drug Administration is not required when the tests are performed in a laboratory licensed by the Clinical Laboratory Improvement Act (CLIA) for high-complexity testing. Such tests must meet the general regulatory standards of CLIA. 


Prior Approval: 


Not applicable.



Chemosensitivity assays, including but not limited to the following are considered investigational for all indications:

  • Histoculture Drug Response Assay (HDRA)
  • Fluorescent Cytoprint Assay
  • ChemoFx Assay
  • CorrectChemo Assay (previously called Microculture Kinetic (Mick) Assay) 

Chemoresistance assays, including but not limited to the following are considered investigational for all indications:

  • Extreme Drug Resistance (EDR) Assays

Based on peer reviewed literature the clinical utility of these assays have not been determined, the data is insufficient to determine whether the use of this testing to select chemotherapy regimens for individual patients will influence patient management decisions and that clinical outcomes are improved. Therefore, tumor chemosensitivity and chemoresistance assay testing is considered investigational for all indications.


Procedure Codes and Billing Guidelines: 

  • To report provider services, use appropriate CPT* codes, Alpha Numeric (HCPCS level 2) codes, Revenue codes, and/or diagnosis codes.
  • 89240 Unlisted miscellaneous pathology test
  • 86849 Unlisted immunology procedure


Selected References: 

  • Samson DJ, Seidenfeld J, Ziegler K et al. Chemotherapy sensitivity and resistance assays: a systematic review. J Clin Oncol 2004; 22(17):3618-30.
  • Loizzi V, Chan JK, Osann K et al. Survival outcomes in patients with recurrent ovarian cancer who were treated with chemoresistance assay-guided chemotherapy. Am J Obstet Gynecol 2003; 189(5):1301-07.
  • Eltabbakh GH. Extreme drug resistance assay and response to chemotherapy in patients with primary peritoneal carcinoma. J Surg Oncol 2000; 73(3):148-52.
  • Mehta RS, Bornstein R, Yu IR. Breast cancer survival and in vitro tumor response in the extreme drug resistance assay. Breast Cancer Res Treat 2001; 66(3):225-37.
  • Holloway RW, Mehta RS, Finkler NJ et al. Association between in vitro platinum resistance in the EDR assay and clinical outcomes for ovarian cancer patients. Gynecol Oncol 2002; 87(1):8-16.
  • Matsuo K, Eno ML, Im DD et al. Clinical relevance of extent of extreme drug resistance in epithelial ovarian carcinoma. Gynecol Oncol 2010; 116(1):61-5.
  • Matsuo K, Bond VK, Eno ML et al. Low drug resistance to both platinum and taxane chemotherapy on an in vitro drug resistance assays predicts improved survival in patients with advanced epithelial ovarian, fallopian and peritoneal cancer. Int J Cancer 2009; 125(11):272-7.
  • Tiersten AD, Moon J, Smith HO et al. Chemotherapy resistance as a predictor of progression-free survival in ovarian cancer patients treated with neoadjuvant chemotherapy and surgical cytoreduction followed by intraperitoneal chemotherapy: a Southwest Oncology Group Study. Oncology 2009; 77(6):395-9.
  • Von Hoff DD, Sandbach JF, Clark GM et al. Selection of cancer chemotherapy for a patient by an in vitro assay versus a clinician. J Natl Cancer Inst 1990; 82(2): 110-6.
  • Iwahashi M, Nakamori M, Nakamura M et al. Individualized adjuvant chemotherapy guided by chemosensitivity test sequential to extended surgery for advanced gastric cancer. Anticancer Res 2005; 25(5):3453-9.
  • Ugurel S, Schadendorf D, Pfohler C et al. In vitro drug sensitivity predicts response and survival after individualized sensitivity-directed chemotherapy in metastatic melanoma: a multicenter phase II trial of the Dermatologic Cooperative Oncology group. Clin Cancer Res 2006; 12(18):5454-63.
  • Karam AK, Chiang JW, Fung E et al. Extreme drug resistance assay results do not influence survival in women with epithelial ovarian cancer. Gynecol Oncol. 2009 Aug;114(2):246-52. Epub 2009 Jun 4.
  • Moon YW, Sohn JH, Kim YT et al. Adenosine triphosphate-based chemotherapy response assay (ATP-CRA)-guided versus empirical chemotherapy in unresectable non-small cell lung cancer. Anticancer Res. 2009 Oct;29(10):4243-9.
  • Herzog TJ, Krivak RC, Fader AN et al. Chemosensitivity testing with ChemoFx and overall survival in primary ovarian cancer. Am J Obstet Gynecol. 2010 Jul;203(1):68.e1-6. Epub 2010 Mar 12.
  • Burstein HJ, Mangu PB, Somerfield MR et al. American Society of Clinical Oncology Clinical Practice Guideline Update on the Use of Chemotherapy Sensitivity and Resistance Assays. J Clin Oncol 2011. Epub ahead of print 2011 Jul 25. doi: 10.1200/JCO.2011.36.0354.
  • National Comprehensive Cancer Network (NCCN) Version 2.2013 Ovarian Cancer
  • Precision Therapeutics, ChemoFx.
  • Diatech Oncology, Microculture Kinetic (MiCK) assay.
  • Hans Neubauer, et. al. Predicting Resistance to Platinum-Containing Chemotherapy with the ATP Tumor Chemosensitivity Assay in Primary Ovarian Cancer. AntiCancer Research 28:949-956 (2008)  
  •      Histoculture Drug Resistance Assay (HDRA) Anticancer Inc., San Diego, CA. ref.html
  • The EVA-PCD® functional profile (Ex Vivo Analysis of Programmed Cell Death), Rationale Therapeutics.
  • The Extreme Drug Resistance assay (EDR Assays ®), Exiqon Diagnostics, Tustin, CA,
  • National Comprehensive Cancer Network (NCCN), Version 3.2014 Ovarian, Fallopian and Primary Peritoneal Cancer.
  • ECRI Institute. Hotline Response. In Vitro Chemosensitivity Assays for Predicting Ovarian Cancer Response to Chemotherapy, July 2014.
  • Centers for Medicare and Medicaid Services, National Coverage Determination (NCD) for Human Tumor Stem Cell drug Sensitivity Assay (190.7).
  • UpToDate. First Line Chemotherapy for advanced (stage II or IV) Epithelial Ovarian, Fallopian Tubal, and Peritoneal Cancer, Thomas J. Herzog, M.D., Deborah K. Armstrong, M.D., Topic last updated April 14, 2014.
  • Linda Bosserman, et al. The Microculture-Kinectic (MiCK) Assay: The Role of a Drug-Induced Apoptosis Assay in Drug Development and Clinical Care, American Association of Cancer Research (AACR), published online first August 3, 2012, DOI:10.1158/0008-5472. CAN-12-0681.
  • National Comprehensive Cancer Network (NCCN) Version 2.2015 Ovarian Cancer. Also available at


Policy History: 

Date                                        Reason                                Action

September 2013                                                                 New policy

August 2014                           Annual review                       Policy revised

July 2015                               Annual review                       Policy revised


Wellmark medical policies address the complex issue of technology assessment of new and emerging treatments, devices, drugs, etc.   They are developed to assist in administering plan benefits and constitute neither offers of coverage nor medical advice. Wellmark medical policies contain only a partial, general description of plan or program benefits and do not constitute a contract. Wellmark does not provide health care services and, therefore, cannot guarantee any results or outcomes. Participating providers are independent contractors in private practice and are neither employees nor agents of Wellmark or its affiliates. Treating providers are solely responsible for medical advice and treatment of members. Our medical policies may be updated and therefore are subject to change without notice.

*Current Procedural Terminology © 2012 American Medical Association. All Rights Reserved.

Contact Information
New information or technology that would be relevant for Wellmark to consider when this policy is next reviewed may be submitted to:
  Wellmark Blue Cross and Blue Shield
  Medical Policy Analyst
  P.O. Box 9232
  Des Moines, IA 50306-9232
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