Efficacy of pembrolizumab in combination with bevacizumab and oral metronomic cyclophosphamide in the treatment of platinum resistant recurrent ovarian cancer: a retrospective observational study.

Objective: To report on the efficacy of pembrolizumab, bevacizumab, and oral metronomic cyclophosphamide used in combination for patients with platinum resistant recurrent ovarian cancer in community practice. Methods: This retrospective observational study was conducted at a single gynecologic oncology practice in Albany, NY. Patients that had a diagnosis of platinum-resistant ovarian cancer (PROC) received intravenous pembrolizumab (200 mg) and bevacizumab (15 mg/kg) every 3 weeks, with oral cyclophosphamide (50 mg) once daily during the treatment cycle until disease progression, toxicity, or withdrawal of consent. Treatment response was determined using imaging and CA-125 levels. Results: Nineteen patients with PROC were included. There were 17 high grade serous and 2 clear cell cancers. Of the 19 patients studied, 10 had Stage IIIC disease at diagnosis. The mean (SD) number of prior lines of treatment was 4.6 (2.0) with 94.7 % of patients having prior exposure to bevacizumab. Four patients had partial responses, 4 had stable disease, and 11 had progressive disease. The objective response rate was 21.1 percent, and the total clinical benefit rate was 42.1 percent. The median progression free survival (PFS) was 4.0 months, and the overall survival (OS) was 17.0 months. The most common adverse events were fatigue (47.4 %), nausea (31.6 %), and abdominal pain (26.3 %). Conclusion: The combination of pembrolizumab, bevacizumab, and oral metronomic cyclophosphamide was well tolerated and demonstrated a 21.1 percent response rate in a heavily pre-treated platinum resistant ovarian cancer population, warranting future investigation of subgroups who may derive benefit from this regimen under such conditions.