Ribociclib and Letrozole Combination Therapy for Ovarian and Endometrial Cancers
Posted: Wednesday, July 17, 2019
Combination therapy consisting of the cyclin-dependent kinases (CDK) 4/6 inhibitor ribociclib and the aromatase inhibitor letrozole appears to be active in patients with estrogen receptor–positive relapsed ovarian or endometrial cancer. Gerardo Colon-Otero, MD, of the Mayo Clinic, Rochester, Minnesota, and colleagues presented these phase II study findings at the 2019 American Society for Clinical Oncology (ASCO) Annual Meeting (Abstract 5510) and published them in the Journal of Clinical Oncology.
A total of 20 patients with relapsed estrogen receptor–positive ovarian cancer and 20 patients with endometrial cancer were enrolled in the study. Patients received a combination of 400 mg of ribociclib plus 2.5 mg of letrozole orally daily. The median age for patients with ovarian cancer was 61 years, and it was 64.5 years for those with endometrial cancer. There were 17 patients with high-grade ovarian serous carcinomas and 3 with low-grade serous carcinomas. Of the patients with endometrial cancer, 11 had endometrioid cancers and 9 had high-grade serous tumors.
After 12 weeks, 10 of the patients with ovarian cancer and 11 of the patients with endometrial cancer were alive without disease progression (progression-free survival of 50% and progression-free survival at 12 weeks of 55%, respectively). Common grade 3 adverse events (occurring in at least 5 patients) included leukopenia (18%), lymphopenia (18%), neutropenia (13%), and fatigue (13%).
Researchers harvested 34 tumor biopsies suitable for injection into mice, and 44% engrafted. Two of the three endometrial cancer xenograft models showed improved progression-free survival with the combination of letrozole and ribociclib compared with letrozole alone.
Disclosure: The study authors’ disclosure information may be found at coi.asco.org.