Clinical relevance of cancer stem cell chemotherapeutic assay for recurrent ovarian cancer

Abstract

Introduction: Disease recurrence and progression of ovarian cancer is common with the development of platinum-resistant or refractory disease. This is due in large part to the presence of chemo-resistant cancer stem cells (CSCs) that contribute to tumor propagation, maintenance, and treatment resistance. We developed a CSCs drug cytotoxicity assay (ChemoID) to identify the most effective chemotherapy treatment from a panel of FDA approved chemotherapies.

Methods: Ascites and pleural fluid samples were collected under physician order from 45 consecutive patients affected by 3rd-5th relapsed ovarian cancer. Test results from the assay were used to treat patients with the highest cell kill drugs, taking into consideration their health status and using dose reductions, as needed. A retrospective chart review of CT and PET scans was used to determine patients' outcomes for tumor response, time to recurrence, progression-free survival (PFS), and overall survival (OS).

Results: We observed that recurrent ovarian cancer patients treated with high-cell kill chemotherapy agents guided by the CSCs drug response assay had an improvement in the median PFS corresponding to 5.4 months (3rd relapse), 3.6 months (4th relapse), and 3.9 months (5th relapse) when compared to historical data. Additionally, we observed that ovarian cancer patients identified as non-responders by the CSC drug response assay had 30 times the hazard of death compared to those women that were identified as responders with respective median survivals of 6 months vs. 13 months. We also found that ChemoID treated patients on average had an incremental cost-effectiveness ratio (ICER) between -$18,421 and $7,241 per life-year saved (LYS).

Conclusions: This study demonstrated improved PFS and OS for recurrent ovarian cancer patients treated with assay-guided chemotherapies while decreasing the cost of treatment.

Keywords: Cancer Stem Cells; ChemoID; Chemotherapeutic Drug Cytotoxicity Assay; Drug Response Assay; Recurrent Ovarian Cancer.

Fig. 1

Limiting dilution transplantation assay in immunodeficient animals. A-C) Necroscopic examination of intraperitoneal tumor nodules observed following injections of 1 × 10² CD44, CD133, or CD117 positive ovarian CSCs, respectively. Arrows point at tumor nodules D) Necroscopic examination of intraperitoneal tumor nodules observed following injections of 1 × 10² ChemoID enriched ovarian CSCs. Arrows point at the several tumor nodules formed. E) Necroscopic examination of intraperitoneal tumor nodules observed following injections of 1 × 10⁶ bulk of tumor ovarian cancer cells. Only one tumor was observed in the control bulk of tumor injected mice.

Fig. 2

Quadrant diagram of the relationship between CSC assay results (%-cell kill on the y-axis) and bulk tumor assay results (%-cell kill on the x-axis) characterized by 6-months recurrence outcomes.

Fig. 3

Kaplan-Meier plots of overall survival across the study period. Overall survival is shown stratified by dichotomized test results for (A) bulk test >55% cell kill - responder or <55% cell kill – non-responder and (B) CSC test >40% cell kill - responder or <40% cell kill – non-responder; Hazard ratios are from Cox proportional hazard models adjusting for number of previous relapses and age.

Fig. 4

Kaplan-Meier plots of progression-free survival across the study period. Progression -free survival is shown stratified by dichotomized test results for (A) bulk test >55% cell kill - responder or <55% cell kill – non-responder and (B) CSC test >40% cell kill - responder or <40% cell kill – non-responder; Hazard ratios are from Cox proportional hazard models adjusting for number of previous relapses and age.

Fig. 5

CT Images and comparative analysis of ChemoID test results on Bulk of Tumor and Cancer StemCells of a patient affected by third recurrence of an ovarian cancer. A) Baseline CT images show presence of large amount of ascites in December of 2016, with B) ovarian mass measuring 9.3 × 5.4 cm, and C) peritoneal carcinomatosis measuring 3.5 × 5.1 cm. D) Comparative ChemoID analysis on Bulk of Tumor and Cancer Stem Cells obtained from fresh ascites aspirate. E) Control CT images in November of 2017 following a Doxorubicin regimen showing regression of ascites, F) smaller ovarian mass measuring 5.8 × 3 cm, and G) smaller peritoneal carcinomatosis measuring 3.4 × 3 cm.