New ovarian cancer immunotherapy study poses question: Can microbiome influence treatment response?

This new study, led by Principal Investigator Emese Zsiros, MD, PhD, FACOG, Assistant Professor of Oncology in Roswell Park's Department of Gynecologic Oncology and Center for Immunotherapy, is a phase II clinical trial that will enroll approximately 40 patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer, and will evaluate the impact of the combination of the PD1-targeting antibody pembrolizumab (Keytruda) with intravenous bevacizumab (Avastin) and oral cyclophosphamide (Cytoxan) on antitumor immune responses and on progression-free survival.

Pembrolizumab has been approved by the U.S. Food and Drug Administration for treatment of advanced melanoma, some metastatic non-small cell lung cancers and recurrent squamous cell head/neck carcinoma, but has only been tested in a small number of ovarian cancer patients, as a single drug and showing modest response. The investigators say a strong scientific rationale supports their hypothesis that the combination of pembrolizumab with two other drugs that have already been approved to treat ovarian cancer -- bevacizumab and low-dose oral cyclophosphamide -- may have much broader benefit for patients.

"Our biggest hope is that by trying these three drugs in combination, we can significantly extend the lives of patients with recurrent ovarian cancer. We also hope to minimize the side effects associated with chemotherapy drugs, and to markedly improve the quality of our patients' lives," says Dr. Zsiros. "We will be looking at potential biomarkers that will tell us who can most benefit from this therapy combination and to better understand how cancer cells and immune cells communicate with one another so that we can design better medications to kill cancer efficiently."

As part of this study, the clinical team will analyze blood, tumor, stool, vaginal and skin microbiome samples, looking to identify possible associations between these markers with clinical outcomes and tumor response. The study, which is supported by a grant from Merck & Co. Inc., maker of pembrolizumab, will be one of the first to analyze these bacteria to determine possible associations with response to immunotherapeutic agents in patients with cancer.

"We're looking at how to improve our immune defenses to cancer, but we're looking at it from a variety of angles," says Dr. Zsiros. "There's a whole new area of research suggesting that what's going on in our gut, our gut flora, has a huge influence on your overall health and happiness, and this study will extend that work into some new directions."

According to the National Cancer Institute, epithelial ovarian cancer is one of the most common gynecologic malignancies, and is the fifth most frequent cause of cancer death in women.