In vitro chemosensitivity assays and in vitro chemoresistance assays have been investigated as a means of predicting the in vivo tumor response to various chemotherapies. A variety of assays have been developed that differ in their processing and in the technique used to measure drug sensitivity. However, typically they involve the same four basic steps:

• Isolation of tumor cells from biopsy specimen,
• Incubation of cells with drugs,
• Assessment of cell survival, and
• Interpretation of the result.

Results may be reported as drug sensitive, drug resistant or intermediate. Drugs identified as drug sensitive are thought to be a potentially effective in vivo chemotherapy. Therefore, clinical use of a chemosensitivity assay involves the positive selection of a type of chemotherapy. This contrasts with chemoresistance assays, which involve the deselection of potentially ineffective drugs. This document addresses in vitro chemosensitivity assays and in vitro chemoresistance assays.

Not Medically Necessary: 

In vitro chemosensitivity assays, as a guide to selection of chemotherapeutic drugs for individuals with cancer, are considered not medically necessary in all cases.

In vitro chemoresistance assays including, but not limited to, extreme drug resistance assays are considered not medically necessary in all cases.

Evidence from available studies is insufficient to conclude that in vitro chemosensitivity testing leads to improved health management or outcomes. The majority of studies reported no survival benefit associated with chemotherapy based on chemosensitivity assays when compared to chemotherapy based on standard regimens or clinical indicators.

Few clinical studies have investigated the value of chemoresistance assays for the selection of chemotherapy. The literature contains only a limited number of randomized controlled trials evaluating the survival rate of individuals treated with assay-directed regimens compared with that of a control group treated with standard regimens.

Cree (2007), in a European multi-center prospective randomized controlled trial, studied tumor chemosensitivity assay directed chemotherapy versus physician's choice in recurrent platinum-resistant ovarian cancer. The primary aim of this trial was to determine response rate and progression free survival following chemotherapy in individuals with platinum resistant recurrent ovarian cancer who had received treatment according to an adenosine triphosphate (ATP) based tumor chemosensitivity assay in comparison with physician's choice. A total of 180 subjects were randomized into two groups with median ages of 59 and 61 years. Ninety-four individuals received assay directed chemotherapy and 86 received physician's choice therapy. The two primary end points studied were response rate and progression-free survival. Response could only be assessed in 147 subjects, and 40.5% achieved a partial or complete response in the assay-directed group versus a 31.5% response in the physician's choice group (P<0.3, not significant). In an intention-to-treat analysis, response rates were 31% in the assay-directed group vs. 26% in the physician choice group. Intention to treat analysis showed a median progression-free survival of 93 days in the physician's choice group and 104 days in the assay-directed group (HR 0.8, not significant). No difference was seen in overall survival between the two groups. The authors concluded the ATP based tumor chemosensitivity assay remains an investigational method in this condition.

Kim and colleagues (2010), in a prospective clinical trial, attempted to determine the most accurate analytic method to define in vitro chemosensitivity and to assess the accuracy of ATP-based chemotherapy response assay (ATP-CRA). Forty-eight individuals with chemo-naïve, histologically confirmed, locally advanced or metastatic gastric cancer were enrolled in this study and treated with combination chemotherapy of paclitaxel 175 mg/m² and cisplatin 75 mg/m² for a maximum of six cycles after obtaining specimen for ATP-CRA. Investigators performed the receiver operator characteristic curve analysis using individual responses by WHO criteria and obtained ATP-CRA results to define the method with the highest accuracy. Median progression free survival was 4.2 months (95% confidence interval [CI]: 3.4-5.0) and median overall survival was 11.8 months (95% CI: 9.7-13.8) for all those enrolled. The chemosensitivity index method demonstrated highest accuracy of 77.8% by ROC curve analysis, and the specificity, sensitivity, positive and negative predictive values were 95.7%, 46.2%, 85.7%, and 75.9%. The in vitro chemosensitive group showed higher response rate (85.7% vs. 24.1%) (P=0.005) compared to chemoresistant group. The authors concluded that ATP-CRA could predict clinical response to paclitaxel and cisplatin chemotherapy with high accuracy in individuals with advanced gastric cancer and results support the use of ATP-CRA in further validation studies and assay-guided clinical trials. However, there were numerous study limitations noted including: the study took almost three years to enroll 36 subjects acceptable for evaluation; many samples were not enrolled due to bacterial contamination and an inadequate amount of tissue; the study was terminated early due to a very poor accrual of subjects, which resulted in an inadequate power to test the accuracy as originally planned; study results needed validation by an independent cohort; the study may have been subject to bias because the clinical response was evaluated in participating centers by investigators who were blind to the in vitro chemosensitivity results but there was no independent review of response evaluation.

There have been several older non randomized studies published involving a microculture kinetic (MiCK) assay and leukemia or lymphoma (Kravtsov, 1994; Kravtsov, 1996; Kravtsov, 1998; Kravtsov, 1999; Liminga, 2000). This assay has been purported to indicate which type of chemotherapy may be most effective against the tumor cells of a particular individual; however, published evidence is insufficient to demonstrate its clinical utility. Most recently, Ballard and colleagues (2010) studied the MiCK assay in endometrial cancer specimens. Endometrial cancer specimens from total abdominal hysterectomies were processed at a central laboratory. Single and combination regimens were tested: combinations of doxorubicin, cisplatin, and paclitaxel and carboplatin and paclitaxel (Gynecologic Oncology Group [GOG] 209 endometrial cancer phase III trial arms) as well as single agent testing with paclitaxel, carboplatin, doxorubicin, cisplatin, ifosfamide, and vincristine (active agents in GOG trials). Apoptosis was measured continuously over 48 hours. Fifteen of 19 individuals were reported to have had successful assays. The highest mean chemo sensitivity was noted in the combination of cisplatin, doxorubicin, and paclitaxel with lower mean chemosensitivity for carboplatin and paclitaxel. Combination chemotherapy had higher chemosensitivity than single drug chemotherapy. However, in 25% of subjects a single drug had higher chemosensitivity than combination chemotherapy. As single agents, ifosfamide, cisplatin, and paclitaxel had the highest kinetic unit values. The authors concluded that MiCK may be useful in future new drug testing and individualizing the chemotherapy management of endometrial cancer. Limitations of this study included a small sample size.

The American Society of Clinical Oncology (ASCO) (2004) does not recommend the use of chemotherapy sensitivity and resistance assays to select chemotherapeutic agents for individuals outside of the clinical trial setting. ASCO cites an insufficient evidence base to support the use in oncology practice.

The National Comprehensive Cancer Network^® (NCCN) clinical practice guidelines include recommendations for ovarian cancer including fallopian tube cancer and primary peritoneal cancer (V2.2011). These guidelines indicate that in vitro chemosensitivity testing to choose a chemotherapy regimen for recurrent disease should not be recommended as there is a lack of demonstrable efficacy for this approach.

At the present time, the clinical utility of in vitro chemosensitivity and chemoresistance assays are unproven. A survival outcome benefit in randomized controlled clinical trials has not been demonstrated.

Chemotherapy sensitivity and resistance assays may also be called human tumor stem cell drug sensitivity assays, nonclonogenic or clonogenic cytotoxic drug resistance assays, tumor stem cell assays, or differential staining cytotoxic assays. These assays are intended to provide oncologists with information which assists in the selection of chemotherapy drugs, to select potentially more effective chemotherapy regimens and to avoid the toxicity of potentially ineffective chemotherapy drugs for an individual.

There are two general types of in vitro assays:
In vitro chemosensitivity assays are proposed to screen potential anticancer drugs, predict the effect of these drugs on tumors and determine the most appropriate chemotherapeutic regimen. The process assumes that the drugs most effective for treating that particular cancer can be identified. Therefore, in vitro chemosensitivity assays involve tumor cells obtained from an individual which are cultured and exposed to specific drugs in the laboratory setting. This process is done over a set period to evaluate survival and resistance of tumor cells to selected drugs. The ineffective drugs, where extreme resistance is exhibited, are eliminated.

In vitro chemoresistance assays propose to provide similar information. In addition, they also are proposed to deselect those drugs that are of no benefit. One of the most widely used techniques is the Extreme Drug Resistance assay (EDR^®). In this assay, cultured cells are exposed to high concentrations of selected chemotherapeutic agents for prolonged periods, far exceeding the exposure anticipated in vivo. Cell lines that survive this exposure are characterized as showing extreme drug resistance. These drugs are then considered potentially ineffective and a physician may be prompted to select another chemotherapeutic agent.

Apoptosis: The innate ability of a cell to undergo programmed death due to detrimental or incompatible derangements in its DNA.

Assay: A test to determine the make-up or potency of a drug.

Cytotoxic drug: Drugs that possess a destructive action on specific cells; often refers to drugs used to fight cancer, such as chemotherapy.

In vitro: Within a glass, petri dish or test tube; in an artificial environment; outside of the body.

In vivo: Within the living body.

The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When Services are Not Medically Necessary:
When the code describes a procedure indicated in the Position Statement section as not medically necessary.

Peer Reviewed Publications:

1. Ballard KS, Homesley HD, Hodson C, et al. Endometrial carcinoma in vitro chemosensitivity testing of single and combination chemotherapy regimens using the novel microculture kinetic apoptosis assay: implications for endometrial cancer treatment. J Gynecol Oncol. 2010; 21(1):45-49.
2. Bosanquet AG, Bell PB. Novel ex vivo analysis of nonclassical, pleiotropic drug resistance and collateral sensitivity induced by therapy provides a rationale for treatment strategies in chronic lymphocytic leukemia. Blood.1996; 87(5):1962-1971.
3. Britten CD, Izbicka E, Hilsenbaeck S, et al. Activity of the multi-targeted antifolate LY231514 in the human tumor cloning assay. Cancer Chemother Pharmacol. 1999; 44(2):105-110.
4. Brown E, Markman M. Tumor chemosensitivity and chemoresistance assays. Cancer 1996; 77(6):1020-1025.
5. Cortazar P, Johnson BE. Review of the efficacy of individualized chemotherapy selected by in vitro drug sensitivity testing for patients with cancer. J Clin Oncol. 1999; 17(5):1625-1631.
6. Cree IA, Kurbacher CM, Lamont A, et al. TCA Ovarian Cancer Trial Group. A prospective randomized controlled trial of tumour chemosensitivity assay directed chemotherapy versus physician's choice in patients with recurrent platinum-resistant ovarian cancer. Anticancer Drugs. 2007 Oct;18(9):1093-1101.
7. Diab SG, Hilsenbeck SG, Izbicka E, et al. Significant activity of a novel cytotoxic agent, LY295501, against a wide range of tumors in the human tumor cloning system. Anticancer Drugs. 1999; 10(3):303-307.
8. Eltabbakh GH, Piver MS, Hempling RE, et al. Correlation between extreme drug resistance and response to primary paclitaxel and cisplatin in patients with epithelial ovarian. Gynecol Oncol. 1998; 70(3):392-397.
9. Hongo T, Yajima S, Sakurai M, et al. In vitro drug sensitivity testing can predict induction failure and early relapse of childhood acute lymphoblastic leukemia. Blood. 1997; 89(8):2959-2965.
10. 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):3453-3459.
11. Kaspers GJ, Veerman AJ, Pieters R, et al. In vitro cellular drug resistance and prognosis in newly diagnosed childhood acute lymphoblastic leukemia. Blood. 1997; 90(7):2723-2729.
12. Kawada K, Yonei, Ueoka H, et al. Comparison of chemosensitivity tests; clonogenic assay versus MTT assay. Acta Med Okayama. 2002; 56(3):129-134.
13. Kim JH, Lee KW, Kim YH, et al. Individualized tumor response testing for prediction of response to Paclitaxel and Cisplatin chemotherapy in patients with advanced gastric cancer. J Korean Med Sci. 2010; 25(5):684-690.
14. Kodera Y, Ito S, Fujiwara M, Mochizuki Y, et al. In vitro chemosensitivity test to predict chemosensitivity for paclitaxel, using human gastric carcinoma tissues. Int J Clin Oncol. 2006 Dec; 11(6):449-453.
15. Kravtsov VD. A novel microculture kinetic assay (MiCK assay) for malignant cell growth and chemosensitivity. Eur J Cancer. 1994; 30A(10):1564-1570.
16. Kravtsov VD, Daniel TO, Koury MJ. Comparative analysis of different methodological approaches to the in vitro study of drug-induced apoptosis. Am J Pathol. 1999; 155(4):1327-1339.
17. Kravtsov VD, Fabian I. Automated monitoring of apoptosis in suspension cell cultures. Lab Invest. 1996; 74(2):557-570.
18. Kravtsov VD, Greer JP, Whitlock JA, Koury MJ. Use of the microculture kinetic assay of apoptosis to determine chemosensitivities of leukemias. Blood. 1998; 92(3):968-980.
19. Liminga G, Martinsson P, Jonsson B, et al. Apoptosis induced by calcein acetoxymethyl ester in the human histiocytic lymphoma cell line U-937 GTB. Biochem Pharmacol. 2000; 60(12):1751-1759.
20. Maenpaa JU, Heinonen E, Hinkka SM, et al. The subrenal capsule assay in selecting chemotherapy for ovarian cancer: a prospective randomized trial. Gynecol Oncol. 1995; 57(3):294-298.
21. Mehta RS, Bornstein R, Yu IR, et al. Breast cancer survival and in vitro tumor response in the extreme drug resistance assay. Breast Cancer Res Treat. 2001; 66(3):225-237.
22. Mollgard L, Prenkert M, Smolowicz A, et al. In vitro chemosensitivity testing of selected myeloid cells in acute myeloid leukemia. Leuk Lymphoma. 2003; 44(5):783-789.
23. O'Toole SA, Sheppard BL, McGuinness EP, et al. The MTS assay as an indicator of chemosensitivity/ resistance in malignant gynaecological tumours. Cancer Detect Prev. 2003; 27(1):47-54.
24. Petit T, Izbicka E, Lawrence RA, et al. Activity of MKT 077, a rhodacyanine dye, against human tumor colony-forming units. Anticancer Drugs. 1999; 10(3):309-315.
25. Petit T, Izbicka E, Lawrence RA, et al. Activity of SCH 66336, a tricyclic farnesyltransferase inhibitor, against human tumor colony-forming units. Ann Oncol. 1999; 10(4):449-453.
26. Raymond E, Hanauske A, Faivre S, et al. Effects of prolonged versus short-term exposure paclitaxel (Taxol) on human tumor colony-forming units. Anticancer Drugs. 1997; 8(4):379-385.
27. Raymond E, Lawrence R, Izbicka E, et al. Activity of oxaliplatin against human tumor colony-forming units. Clin Cancer Res. 1998; 4(4):1021-1029.
28. Sharma S, Neal MH, Di Nicolantonio F, et al. Outcome of ATP-based tumor chemosensitivity assay directed chemotherapy in heavily pre-treated recurrent ovarian carcinoma. BMC Cancer. 2003; 3(1):19.
29. Silber R, Degar B, Costin D, et al. Chemosensitivity of lymphocytes from patients with B-cell chronic lymphocytic leukemia to chlorambucil, fludarabine, and camptothecin analogs. Blood. 1994; 84(10):3440-3446.
30. 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):5454-5463.

Government Agency, Medical Society, and other Authoritative Publications:

1. Blue Cross and Blue Shield Association. Chemotherapy sensitivity and resistance assays. TEC Assessment. October 2002; 17(2).
2. Centers for Medicare and Medicaid Services. National Coverage Decision for Human Tumor Stem Cell Drug Sensitivity Assays (190.7). Available at: http://www.cms.hhs.gov/mcd/index_list.asp?list_type=ncd. Accessed on March 21, 2011.
3. National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology. V.2.2011. Ovarian Cancer Including Fallopian Tube Cancer and Primary Peritoneal Cancer. For additional information: http://www.nccn.org. Accessed on March 21, 2011.
4. Schrag, D, Garewal HS, Burstein HJ, et al. American Society of Clinical Oncology Technology Assessment: chemotherapy sensitivity and resistance assays. J Clin Oncol. 2004; 22(17):3631-3638.

Chemotherapy Sensitivity and Resistance Assays
ChemoFx^® Assay
Clonogenic Cytotoxic Drug Resistance Assays
Cytoprint
Differential Staining Cytotoxic Assays
Extreme Drug Resistance Assay (EDR)
Human Tumor Stem Cell Drug Sensitivity Assays
Microculture Kinetics (MiCK) assay
MTT Assay
Nonclonogenic Clonogenic Cytotoxic Drug Resistance Assays
Tumor Stem Cell Assays

The use of specific product names is illustrative only.  It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.