Results from a new Phase 3 trial published in the journal npj Precision Oncology found that a cancer stem cell test can accurately choose more effective treatments and lead to improved outcomes for patients with platinum-resistant ovarian cancer.

The University of Cincinnati Cancer Center’s Thomas Herzog, MD, the study’s first author, said epithelial ovarian cancer often initially responds to chemotherapy treatment and then enters a period of resistance to therapy and tumor regrowth.

“This is partly due to the selection and reactivation of cancer stem cells (CSCs) that rebuild and repair the tumor from the damage received from chemotherapy,” said Herzog, a Cancer Center physician researcher, the Paul and Carolyn Flory Professor in Gynecologic Oncology in the UC College of Medicine and director of UC Health’s Gynecologic Cancer Disease Center.

Pier Paolo Claudio, MD, who codeveloped the clinical test, said the ChemoID platform challenges the CSCs found in individual patients’ tumors against specific anticancer drugs to identify which drugs are likely to be the most effective.

“The thought is that by testing the tumor for chemosensitivity in not only the tumor cells, but also the cancer stem cells, one can eradicate the CSCs that would repopulate the tumor,” Herzog said.

The 81 patients with platinum-resistant ovarian cancer (cancer recurrence within six months of receiving a platinum-based chemotherapy) enrolled in the trial were randomized to have the choice of chemotherapy treatment decided through ChemoID or to have physicians choose using standard methods. Herzog said doctors selecting treatments typically rely on approved therapies, past experiences, patients’ prior treatments, and toxicity or side effects patients have already experienced.

Researchers’ primary measurement was the patients’ objective response rate (ORR), or the percentage of patients in each treatment group who had a partial or complete response to the treatment within a certain period of time. Additionally, they measured progression-free survival (PFS)—the length of time during and after treatment that a patient lives without the cancer getting worse—and duration of response.

“Overall response rate, median progression-free survival and median duration of response were statistically and clinically significantly improved when patients were treated using the ChemoID assay versus physician’s choice therapy in a randomized trial of patients with recurrent ovarian cancer,” Herzog said.

The ORR of patients in the ChemoID arm was 50%, compared to 5% for patients in the physician-choice arm. Median PFS for patients in the ChemoID arm was 11 months, compared to a median of three months for the physician-choice arm. ChemoID patients had a median duration of response of eight months, compared to five-and-a-half months for physician-choice.

Improved patient response rates to treatments could potentially reduce health care costs related to ineffective therapies and unnecessary toxicity, Claudio said. This study’s findings suggest that utilizing assay-guided treatments may relieve financial toxicity, especially for ovarian cancer patients with platinum-resistant disease, who face significant challenges in treatment selection.

Moving forward, Herzog said additional data is needed to further validate ChemoID and better understand how it works within certain molecular subgroups, such as patients with BRCA mutations. Testing new, emerging biologic therapies will also further refine the best uses for the test.