Ribociclib plus letrozole elicits responses in patients with recurrent low-grade serous carcinoma of the ovary, fallopian tube, or peritoneum, according to trial results presented at the 2023 SGO Annual Meeting on Women’s Cancer.
In this phase 2 trial, patients who received ribociclib plus letrozole had an overall response rate (ORR) of 23%. This is higher than, or equivalent to, ORRs observed in previous trials, said study presenter Brian M. Slomovitz, MD, of Mount Sinai Medical Center in Miami Beach, Florida.
The current trial (ClinicalTrials.gov Identifier: NCT03673124) included 48 evaluable patients with recurrent low-grade serous carcinoma of the ovary, fallopian tube, or peritoneum.
The patients’ median age was 58.5 (range, 21-85) years. Most (73%) had received chemotherapy, 27% had received hormonal therapy, and 13% had received immunotherapy. None of the patients had received prior letrozole or a CDK4/6 inhibitor.
After trial enrollment, the patients received letrozole at 2.5 mg daily. They received ribociclib at 600 mg daily in a 3 weeks on, 1 week off schedule.
At the data cutoff, 38% of patients remained on study. The reasons for discontinuation were progression (n=17), withdrawal (n=5), death (n=3), toxicity (n=2), and other reasons (n=3).
The ORR was 23%, and all 11 responders had partial responses. The median time to response was 7.9 months, and the median duration of response (DOR) was 19.1 months.
The clinical benefit rate was 79%. The median progression-free survival (PFS) was 19.1 months, and the median overall survival was not reached.
The most common grade 3 or higher adverse events were neutrophil count decrease (44%), white blood cell count decrease (8%), and anemia (4%).
Dr Slomovitz compared efficacy outcomes in this trial with efficacy outcomes from other clinical trials of patients with recurrent low-grade serous carcinoma of the ovary, fallopian tube, or peritoneum.
The ORR in the current trial (23%) was superior to the ORRs in 5 treatment arms from 3 other trials (range, 6%-16%). In addition, the ORR in the current trial was comparable to the ORR in patients who received trametinib (26%) in the GOG 281/LOGS trial.
The current trial also had a superior DOR (median, 19.1 months) when compared with the other trial arms (range, 5.9-13.6 months) and superior PFS (median, 19.1 months) when compared with the other trial arms (range, 7.2-13.0 months).
“Ribociclib and letrozole is an active combination in patients with low-grade serous carcinoma,” Dr Slomovitz said in closing. “The overall response rate, progression-free survival, and duration of response compare favorably to the most active agents previously investigated.”
Disclosures: This research was supported by Novartis. Dr Slomovitz disclosed relationships with AstraZeneca, Eisai, Genentech, Genmab, GlaxoSmithKline, Karyopharm, Imvax, Incyte, Merck, Myriad, Onconova, and Seagen.
Slomovitz BM, Deng W, Killion J, et al. GOG 3026: A phase II trial of letrozole + ribociclib in women with recurrent low-grade serous carcinoma of the ovary, fallopian tube or peritoneum (LGSOC): A GOG Foundation study. SGO 2023. March 25-28, 2023.