Selection of appropriate chemotherapy, including identification of platinum resistance, is critical to effective management of advanced epithelial ovarian cancer (EOC). ChemoFx®, a multiple treatment marker (chemoresponse assay), has been developed to address this challenge and to improve outcomes in patients with advanced EOC. While much work has been done that has demonstrated the analytical validity of this assay, more recent studies have highlighted the unique clinical benefits offered by the assay. A prospective, multicenter trial has shown an increase in overall survival (OS) of 14 months and an increase in progression-free survival (PFS) by 3 months in patients with recurrent EOS treated by a “sensitive” therapy based on ChemoFx results. Along with other studies showing similar gains in OS and PFS, ChemoFx has been shown to be both a prognostic and predictive marker in patients with recurrent EOC where current treatment options are sorely lacking. In addition to these clinical benefits, economic analyses have shown that ChemoFx is a cost-effective intervention. Current guidelines and technology assessments relating to ChemoFx are largely outdated and refer primarily to metrics of analytical validity. Thus, in addition to analytical validity, the clinical validity, clinical utility and economic impact of ChemoFx are reviewed herein, including published literature, technology assessments by independent parties, and regulatory approvals of this marker.
Funding StatementNo outside funding was provided for this review.
Aggressive cytoreductive surgery followed by platinum-based chemotherapy is the standard first-line approach for the management of EOC. Currently, 6 different first-line chemotherapy regimens are recommended options in the National Comprehensive Cancer Network (NCCN) guidelines for Ovarian Cancer.1 Patient outcomes, however, are similar among the recommended options. Intravenous (IV) carboplatin/paclitaxel is the most commonly used regimen. While 60-80% of patients initially respond to this standard approach, the median PFS remains just 17 months and the median OS is 44 months.2 Therefore, in practically all women, the disease returns despite initial response to chemotherapy.
Selecting optimally effective treatment(s) for recurrent EOC is challenging. Considerations include: site(s) of recurrence, patient comorbidities, and cumulative toxicity from first-line chemotherapy. Repeat cytoreductive surgery and second-line chemotherapy are the most common treatments for recurrent or persistent disease. While most patients eventually succumb to EOC, many will experience prolonged remissions and symptom-free survival.3,4 Relapses in patients occurring more than 6 months from the completion of first-line therapy are considered to be ‘platinum-sensitive’. A portion of these patients will respond to re-exposure to platinum-based therapy. However, treatment guidelines outline numerous platinum-based regimens,1 with little or no difference in clinical performance for the population across the various options. Patients who progress during treatment or within 6 months of completion of first-line therapy are considered to be ‘platinum-resistant’, and decisions regarding second-line treatment are especially difficult. Platinum-resistant EOC is typically treated with sequential non-platinum single agent therapies. In general, the PFS and OS are poor for this group of patients compared to those who manifest platinum-sensitive disease. Currently, the treatment of EOC remains largely empiric. As with most clinical factors, the accuracy of platinum sensitivity and resistance is not absolute, and additional measures of responsiveness may be beneficial in personalizing treatment strategies.
As defined by the National Institutes of Health (NIH), a marker is “a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention”.5 Therefore, ChemoFx is considered a marker of multiple treatments and provides tumor-specific information to assist physicians in the selection of effective chemotherapy for individual patients with gynecologic cancers. ChemoFx is intended to be utilized in conjunction with treatment guidelines, heuristics and pathways. Physicians indicate which of the multiple, guideline-recommended, FDA-approved chemotherapy options are under consideration for each patient when ordering the assay, and ChemoFx reports a result for each of the single agent or combination treatments selected for testing.
ChemoFx is a cell culture-based chemoresponse assay that measures the sensitivity of tumor-derived malignant epithelial cells to chemotherapeutic agents in vitro, using quantification of cellular DNA as the assay endpoint.6 The assay employs tumor tissue samples available at the time of clinically indicated surgery, biopsy or paracentesis; so, no additional procedures are required to fulfill tissue collection requirements for the assay. Tissue is shipped to the ChemoFx laboratory (Helomics™ Corporation, Pittsburgh, PA), and primary cultures are initiated by mincing each tissue sample into 1 mm3explants, which are then seeded into culture flasks. Upon near confluency, primary cultures are trypsinized and seeded into 384-well microtiter plates and used immediately for in vitro testing. Multiple concentrations of each treatment are prepared by serial dilution. Each concentration is added to three replicate wells on the microtiter plate; three replicates of control (no treatment) wells are also associated with each treatment. Culture seeding into microtiter plates, as well as serial treatment dilution and application, are completed using highly automated liquid handling robotics ensuring a consistent and repeatable process.7 After 72 hours of incubation with treatment, DNA in the nucleus of surviving adherent cells is stained with DAPI and counted using proprietary, automated, computer-assisted microscopy.7 The inhibition of tumor growth is measured for each concentration (average of cell counts in three replicates) of a given treatment. The survival fraction (SF) of tumor cells at each concentration is calculated as compared to control.8 The summation of SF values is computed as the drug response score, which represents the area under the dose response curve (AUC). A smaller AUC score indicates that a tumor is more sensitive to a treatment in vitro; a larger score indicates greater resistance to a treatment. For each treatment, in vitro tumor response is classified into one of three categories according to the AUC score: sensitive (S), intermediate sensitive (IS), or resistant (R). The cut-point threshold for the classifications were previously and independently established based on the 25th and 75th AUC percentiles in referent specimens, with an AUC score less than 25th rank classified as S, between 25th and 75th rank as IS, and greater than 75th rank as R.
Unique, Distinguishing Features of ChemoFx
ChemoFx is distinguished from prior chemoresponse assays in a number of ways:
While ChemoFx is more a phenotypic, than a typical genomics assay, it represents the phenotypic response represents an integrated manifestation of genetic, genomic, proteomic and functional characteristics of a tumor. Published studies suggest that ChemoFx represents a novel platform for multigene (microarray) signature development, by associating in vitro assay response data with gene expression profiling data.9,10,11 Specifically, a multigene signature developed utilizing the ChemoFx platform has been independently validated, differentiating pathologic complete response from residual disease after neoadjuvant chemotherapy.9 The ability of ChemoFx to simultaneously assess response to multiple therapies makes this assay especially useful for developing genomic signatures that may predict differential response to therapies.
Public Health Importance
It is estimated that, in 2015, there will be 21,290 new cases of ovarian cancer and 14,180 deaths due to this disease in the United States; EOC represents the leading cause of death from gynecologic cancer.12 The poor prognosis observed with EOC is largely attributed to detection of the disease at an advanced stage, as well as drug resistance at initial presentation or developed later. Although standard first-line treatment is initially effective for the majority of EOC patients, most of these patients will relapse within 1-2 years, and only 30% will live beyond 5 years.13Given this unfortunate prognosis, there is a strong desire, as well as clinical opportunity, to extend the overall survival of EOC patients. More than 30 different acceptable treatment choices are identified in current treatment guidelines for recurrent EOC.1 Yet, evidence on a population-wide level is insufficient to show that any one of the recommended regimens is superior to any others. ChemoFx can help guide personalized therapy decisions through the phenotypic approach of a chemoresponse assay. Further, in EOC, unlike some other solid tumors, biomarkers have not been well validated to document their ability to stratify patients for individualized treatment choices that improve outcomes. Recently published clinical trials provide evidence in support of the analytical validity, clinical validity and clinical utility of ChemoFx and are described in detail below. These new studies, including the first prospective clinical trials examining a chemoresponse assay, are published in the context of a significant of negative reviews of chemoresponse assays due to lack of prospectively designed clinical trials. These new studies address a need for validation proven through prospective clinical trials which has been requested for a number of years.
Published Reviews, Recommendations and Guidelines
Systemic evidence reviews/technology assessments
The Blue Cross Blue Shield Association Technology Evaluation Center (BCBS TEC) evaluated chemoresponse assays in 1995 and subsequently issued minor updates in 2000 and 2002. BCBS TEC found that chemoresponse assays do not meet all of the TEC criteria, primarily due to a lack of prospective, randomized clinical trials to compare the outcomes of assay-guided treatment and empiric treatment.14,15,16 More than a decade has passed since the most recent BCBS TEC evaluation of 2002. Since then, multiple clinical trials, both retrospective and prospective, have reported on the clinical validity and clinical utility of ChemoFx,17,18,19,20,21,22,23 and, as such, these data were not included in any of the BCBS TEC assessments.
The American Society of Clinical Oncology (ASCO) also published technology assessments of chemoresponse assays in 2004 and 2011, with consideration of literature published through May 2010 for the 2011 assessment.24,25 Both ASCO assessments concluded that the then-current clinical literature did not support use of chemoresponse assays in routine oncology practice, citing low success rates, lack of appropriate prospective evaluation in clinical trials and a tendency to simply recommend treatments that would have been given empirically (i.e. low utility).24 However, the assessments noted the potential importance and impact of these assays and encouraged participation in clinical trials evaluating chemoresponse assays. It is, once again, noteworthy that the ASCO technology assessments were conducted prior to the publication of key clinical validations of ChemoFx which demonstrate the high technical success of ChemoFx compared to other CSRAs, prospective evaluation of the assay, and clinical utility by comparing clinical outcomes of patients with and without access to the assay.18,19,20,21,22,23Specific details of these studies are noted below.
Recommendations by independent groups
The Helomics laboratory, where ChemoFx is performed, has undergone a number of evaluations of its analytical validity. The Wadsworth Center of the State of New York performed an independent review of the technology, standard operating procedures, quality measures, and analytical and clinical validation results of ChemoFx, resulting in approval and licensure in the state of New York. Furthermore, ChemoFx testing is performed in the Helomics Corporation laboratory in Pittsburgh, Pennsylvania, which is certified to comply with the Centers for Medicare & Medicaid Services Clinical Laboratory Improvement Amendments (CLIA) program. The ChemoFx laboratory is licensed by CLIA nationwide and also has specified licensure by the states of New York, California, Florida, Maryland, Pennsylvania and Rhode Island.
Guidelines by professional groups
In 2010, the NCCN Clinical Practice Guidelines in Oncology for Ovarian Cancer: Including Fallopian Tube Cancer and Primary Peritoneal Cancer were amended to state that “Chemosensitivity/resistance and/or other biomarker assays are being used in some NCCN Member Institutions for decisions related to future chemotherapy in situations where there are multiple equivalent chemotherapy options available.” Use of chemoresponse assays is classified as a category 3 level of evidence and has not been re-evaluated by the NCCN since 2010. ChemoFx has been used in 20 of 21 NCCN institutions. As with the above two situations the, this was completed before the most recent round of publications.
Clinical Utility and Other Supportive Studies
Although a prospective, randomized controlled trial design has been recommended for use in the validation of markers due to its successful use in the validation of drugs, it is suggested that alternate study designs may be more appropriate for evaluating markers (especially tests that have the ability to report multiple markers simultaneously) which interface with and impact clinical scenarios differently than drugs.29,30 As such, clinical validations of ChemoFx employ a study design based on the marker-stratified (non-randomized, blinded) approach that has been successfully used in the validations of several markers that are considered to be standards of care in oncology (e.g. KRAS, Oncotype DX®, VeriStrat®).31,32,33,34,35,36,37 This approach overcomes the pragmatic obstacles of the design recommended in technology assessments (e.g. large sample size, heterogeneity of possible therapies) while allowing evaluation of multiple markers simultaneously and evaluating a marker’s predictive properties.
Although ChemoFx provides relative effectiveness within a given therapy (as compared to like patients), the comparative effectiveness between multiple therapies is not considered. Furthermore, other factors which influence treatment selection (e.g. toxicity) are not considered in the ChemoFx results, but remain as independent components of the patient’s profile that the physician considers when selecting the appropriate course of therapy.
Outcomes for women with gynecologic cancers who have been empirically treated are stagnant and disappointing. ChemoFx helps clinicians individualize treatment selections and improve patient outcomes in gynecologic cancer. Numerous publications have outlined the strength of the analytical validity behind the ChemoFx assay in this setting. Several more recent studies, including those with a prospective design, have clinically validated that ChemoFx is an assay capable of predicting the effectiveness of specific therapies and that patients treated with ChemoFx sensitive therapies experience improved outcomes. Patients experienced improvements in OS of up to 14 months when treatments sensitive in ChemoFx were used clinically. Benefits of using ChemoFx, however, are not only limited to increases in OS and PFS. By limiting treatment with ineffective therapies, patients experience fewer unnecessary adverse effects and drug-related toxicities. These factors contribute to the evidence that has shown use of ChemoFx results in reduced overall treatment costs when compared to the current empiric based standard of care. The current evidence strongly suggests that ChemoFx provides a compelling and exciting option for improving the treatment paradigm and patient outcomes in EOC.
SR is a paid member of Helomics Corporation’s speakers bureau. AW is a paid consultant for Helomics Corporation and holds stock options with the company.
AcknowledgementsWe thank Aledo Consulting, Inc. for critical review of this manuscript.
- National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Ovarian Cancer: Including Fallopian Tube Cancer and Primary Peritoneal Cancer. Version 1.2015. Accessed March 2, 2015.
- Bookman MA, Brady MF, McGuire WP, Harper PG, Alberts DS, Friedlander M, Colombo N, Fowler JM, Argenta PA, De Geest K, Mutch DG, Burger RA, Swart AM, Trimble EL, Accario-Winslow C, Roth LM. Evaluation of new platinum-based treatment regimens in advanced-stage ovarian cancer: a Phase III Trial of the Gynecologic Cancer Intergroup. J Clin Oncol. 2009 Mar 20;27(9):1419-25. PubMed PMID:19224846.
- Thigpen T. A rational approach to the management of recurrent or persistent ovarian carcinoma. Clin Obstet Gynecol. 2012 Mar;55(1):114-30. PubMed PMID:22343233.
- Cooke SL, Brenton JD. Evolution of platinum resistance in high-grade serous ovarian cancer. Lancet Oncol. 2011 Nov;12(12):1169-74. PubMed PMID:21742554.
- Biomarkers and surrogate endpoints: preferred definitions and conceptual framework. Clin Pharmacol Ther. 2001 Mar;69(3):89-95. PubMed PMID:11240971.
- Heinzman JM, Brower SL, Bush JE, Silverman JF. Ex vivo enrichment of malignant carcinoma cells in primary culture. Pathology. 2007 Oct;39(5):491-4. PubMed PMID:17886099.
- Heinzman JM, Rice SD, Corkan LA. Robotic liquid handlers and semiautomated cell quantification systems increase consistency and reproducibility in high-throughput, cell-based assay. JALA 2010;15:7-15.
- Brower SL, Fensterer JE, Bush JE. The ChemoFx assay: an ex vivo chemosensitivity and resistance assay for predicting patient response to cancer chemotherapy. Methods Mol Biol. 2008;414:57-78. PubMed PMID:18175812.
- Shen K, Qi Y, Song N, Tian C, Rice SD, Gabrin MJ, Brower SL, Symmans WF, O'Shaughnessy JA, Holmes FA, Asmar L, Pusztai L. Cell line derived multi-gene predictor of pathologic response to neoadjuvant chemotherapy in breast cancer: a validation study on US Oncology 02-103 clinical trial. BMC Med Genomics. 2012 Nov 16;5:51. PubMed PMID:23158478.
- Shen K, Rice SD, Gingrich DA, Wang D, Mi Z, Tian C, Ding Z, Brower SL, Ervin PR Jr, Gabrin MJ, Tseng G, Song N. Distinct genes related to drug response identified in ER positive and ER negative breast cancer cell lines. PLoS One. 2012;7(7):e40900. PubMed PMID:22815861.
- Shen K, Song N, Kim Y, Tian C, Rice SD, Gabrin MJ, Symmans WF, Pusztai L, Lee JK. A systematic evaluation of multi-gene predictors for the pathological response of breast cancer patients to chemotherapy. PLoS One. 2012;7(11):e49529. PubMed PMID:23185353.
- Siegel RL, Miller KD, Jemal A. Cancer statistics, 2015. CA Cancer J Clin. 2015 Jan-Feb;65(1):5-29. PubMed PMID:25559415.
- Coleman RL, Monk BJ, Sood AK, Herzog TJ. Latest research and treatment of advanced-stage epithelial ovarian cancer. Nat Rev Clin Oncol. 2013 Apr;10(4):211-24. PubMed PMID:23381004.
- Blue Cross and Blue Shield Association. Nonclonogenic cytotoxic drug resistance assay. Technology Evaluation Center Assessment Program 1995;10(22).
- Blue Cross and Blue Shield Association. Chemotherapy sensitivity and resistance assays. Technology Evaluation Center Assessment Program 2000;15(11).
- Blue Cross and Blue Shield Association. Chemotherapy sensitivity and resistance assays. Technology Evaluation Center Assessment Program 2002;17(12).
- Gallion H, Christopherson WA, Coleman RL, DeMars L, Herzog T, Hosford S, Schellhas H, Wells A, Sevin BU. Progression-free interval in ovarian cancer and predictive value of an ex vivo chemoresponse assay. Int J Gynecol Cancer. 2006 Jan-Feb;16(1):194-201. PubMed PMID:16445633.
- Herzog TJ, Krivak TC, Fader AN, Coleman RL. Chemosensitivity testing with ChemoFx and overall survival in primary ovarian cancer. Am J Obstet Gynecol. 2010 Jul;203(1):68.e1-6. PubMed PMID:20227055.
- Rutherford T, Orr J Jr, Grendys E Jr, Edwards R, Krivak TC, Holloway R, Moore RG, Puls L, Tillmanns T, Schink JC, Brower SL, Tian C, Herzog TJ. A prospective study evaluating the clinical relevance of a chemoresponse assay for treatment of patients with persistent or recurrent ovarian cancer. Gynecol Oncol. 2013 Nov;131(2):362-7. PubMed PMID:23954900.
- Krivak TC, Lele S, Richard S, Secord AA, Leath CA 3rd, Brower SL, Tian C, Moore RG. A chemoresponse assay for prediction of platinum resistance in primary ovarian cancer. Am J Obstet Gynecol. 2014 Jul;211(1):68.e1-8. PubMed PMID:24530815.
- Tian C, Sargent DJ, Krivak TC, Powell MA, Gabrin MJ, Brower SL, Coleman RL. Evaluation of a chemoresponse assay as a predictive marker in the treatment of recurrent ovarian cancer: further analysis of a prospective study. Br J Cancer. 2014 Aug 26;111(5):843-50. PubMed PMID:25003664.
- Grendys EC Jr, Fiorica JV, Orr JW Jr, Holloway R, Wang D, Tian C, Chan JK, Herzog TJ. Overview of a chemoresponse assay in ovarian cancer. Clin Transl Oncol. 2014 Sep;16(9):761-9. PubMed PMID:24986099.
- Plamadeala V, Kelley JL, Chan JK, Krivak TC, Gabrin MJ, Brower SL, Powell MA, Rutherford TJ, Coleman RL. A cost-effectiveness analysis of a chemoresponse assay for treatment of patients with recurrent epithelial ovarian cancer. Gynecol Oncol. 2015 Jan;136(1):94-8. PubMed PMID:25462203.
- Schrag D, Garewal HS, Burstein HJ, Samson DJ, Von Hoff DD, Somerfield MR. American Society of Clinical Oncology Technology Assessment: chemotherapy sensitivity and resistance assays. J Clin Oncol. 2004 Sep 1;22(17):3631-8. PubMed PMID:15289488.
- Burstein HJ, Mangu PB, Somerfield MR, Schrag D, Samson D, Holt L, Zelman D, Ajani JA. American Society of Clinical Oncology clinical practice guideline update on the use of chemotherapy sensitivity and resistance assays. J Clin Oncol. 2011 Aug 20;29(24):3328-30. PubMed PMID:21788567.
- Mi Z, Holmes FA, Hellerstedt B, Pippen J, Collea R, Backner A, Bush JE, Gallion HH, Wells A, O'Shaughnessy JA. Feasibility assessment of a chemoresponse assay to predict pathologic response in neoadjuvant chemotherapy for breast cancer patients. Anticancer Res. 2008 May-Jun;28(3B):1733-40. PubMed PMID:18630452.
- Dalton HJ, Fiorica JV, Edwards RP, Benjamin I, Rocconi RP, Recio FO, Lovecchio JL, Burrell MO, Shahin MS, Grendys EC, Wang D, Wang T, Monk BJ. In vitro chemoresponse in metachronous pairs of ovarian cancers. Anticancer Res. 2014 Dec;34(12):7191-6. PubMed PMID:25503148.
- Havrilesky LJ, Krivak TC, Mucenski JW, Myers ER. Impact of a chemoresponse assay on treatment costs for recurrent ovarian cancer. Am J Obstet Gynecol. 2010 Aug;203(2):160.e1-7. PubMed PMID:20417480.
- Freidlin B, McShane LM, Korn EL. Randomized clinical trials with biomarkers: design issues. J Natl Cancer Inst. 2010 Feb 3;102(3):152-60. PubMed PMID:20075367.
- Center for Medical Technology Policy. Evaluation of clinical validity and clinical utility of actionable molecular diagnostic tests in adult oncology. May 1, 2013.
- Amado RG, Wolf M, Peeters M, Van Cutsem E, Siena S, Freeman DJ, Juan T, Sikorski R, Suggs S, Radinsky R, Patterson SD, Chang DD. Wild-type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer. J Clin Oncol. 2008 Apr 1;26(10):1626-34. PubMed PMID:18316791.
- Karapetis CS, Khambata-Ford S, Jonker DJ, O'Callaghan CJ, Tu D, Tebbutt NC, Simes RJ, Chalchal H, Shapiro JD, Robitaille S, Price TJ, Shepherd L, Au HJ, Langer C, Moore MJ, Zalcberg JR. K-ras mutations and benefit from cetuximab in advanced colorectal cancer. N Engl J Med. 2008 Oct 23;359(17):1757-65. PubMed PMID:18946061.
- Paik S, Shak S, Tang G, Kim C, Baker J, Cronin M, Baehner FL, Walker MG, Watson D, Park T, Hiller W, Fisher ER, Wickerham DL, Bryant J, Wolmark N. A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. N Engl J Med. 2004 Dec 30;351(27):2817-26. PubMed PMID:15591335.
- Paik S, Tang G, Shak S, Kim C, Baker J, Kim W, Cronin M, Baehner FL, Watson D, Bryant J, Costantino JP, Geyer CE Jr, Wickerham DL, Wolmark N. Gene expression and benefit of chemotherapy in women with node-negative, estrogen receptor-positive breast cancer. J Clin Oncol. 2006 Aug 10;24(23):3726-34. PubMed PMID:16720680.
- Carbone DP, Ding K, Roder H, Grigorieva J, Roder J, Tsao MS, Seymour L, Shepherd FA. Prognostic and predictive role of the VeriStrat plasma test in patients with advanced non-small-cell lung cancer treated with erlotinib or placebo in the NCIC Clinical Trials Group BR.21 trial. J Thorac Oncol. 2012 Nov;7(11):1653-60. PubMed PMID:23059783.
- Gregorc V, Novello S, Lazzari C, Barni S, Aieta M, Mencoboni M, Grossi F, De Pas T, de Marinis F, Bearz A, Floriani I, Torri V, Bulotta A, Cattaneo A, Grigorieva J, Tsypin M, Roder J, Doglioni C, Levra MG, Petrelli F, Foti S, Viganò M, Bachi A, Roder H. Predictive value of a proteomic signature in patients with non-small-cell lung cancer treated with second-line erlotinib or chemotherapy (PROSE): a biomarker-stratified, randomised phase 3 trial. Lancet Oncol. 2014 Jun;15(7):713-21. PubMed PMID:24831979.
- Stinchcombe TE, Roder J, Peterman AH, Grigorieva J, Lee CB, Moore DT, Socinski MA. A retrospective analysis of VeriStrat status on outcome of a randomized phase II trial of first-line therapy with gemcitabine, erlotinib, or the combination in elderly patients (age 70 years or older) with stage IIIB/IV non-small-cell lung cancer. J Thorac Oncol. 2013 Apr;8(4):443-51. PubMed PMID:23370367.