Ribociclib Data Show Reduced Mortality Risk in HR+/HER2- Advanced Breast Cancer

Postmenopausal women with hormone-receptor positive, human epidermal growth factor receptor-2 negative (HR+/HER2–) breast cancer treated initially with ribociclib plus fulvestrant saw overall survival (OS) benefits of nearly 16 more months than those treated with fulvestrant alone, according to new results of a groundbreaking trial.

Patients treated with ribociclib, a CDK4/6 inhibitor sold as Kisqali, achieved a 33% reduction in the risk of death and a medial OS of 67.6 months, according to the exploratory analysis from MONALEESA-3, which was unveiled May 4 during the European Society for Medical Oncology (ESMO) Breast Cancer Congress.

The initial study was presented at ESMO Congress 2019 and published in the New England Journal of Medicine. According to a statement from Novartis, which makes ribociclib and funded the study, the final OS analysis demonstrated a statistically significant OS benefit for ribociclib in combination with fulvestrant and a relative reduction in the risk of death by 28% vs fulvestrant alone in the full population (HR, 0.72; 95% CI: 0.568-0.924; P = .00455).

“MONALEESA-3 results continue to demonstrate the survival benefit of treatment with ribociclib for postmenopausal women with advanced breast cancer,” senior author Dennis J. Slamon, MD, director of clinical/translational research, University of California, Los Angeles Jonsson Comprehensive Cancer Center, said in a statement. “Whether partnered with fulvestrant or an aromatase inhibitor in the first-line setting, ribociclib offers oncologists a CDK4/6 inhibitor with consistent benefit in providing women with HR+/HER2– advanced breast cancer more quality time, regardless of their disease characteristics.”

Officials from Novartis emphasized that the ribociclib/fulvestrant combination is the only one in the CDK4/6 inhibitor class to demonstrate an OS benefit when used in a first-line setting. The combination has also produced the longest median OS, which has been reported in 3 phase 3 trials.

In MONALEESA-3, postmenopausal patients were randomized 2:1 to receive the ribociclib/fulvestrant combination or a placebo with fulvestrant. In this update, investigators reported an exploratory analysis of OS with additional follow-up, “allowing further characterization of long-term OS benefits of [ribociclib] in the [first-line] setting.”

At the data cutoff of January 12, 2022, the median follow-up for patients treated in the first-line setting was 70.8 months; 16.5% and 8.6% of patients remained in the treatment and placebo arms, respectively. An OS benefit was seen in those treated first-line with ribociclib vs placebo (median OS, 67.6 vs 51.8 months) for a hazard ratio of 0.67 (95% CI, 0.50-0.90). The OS rate at 5 years was 56.6% vs 42.1%, favoring ribociclib. Progression-free survival 2, which is time from randomization to second disease progression or death, also favored ribociclib (HR, 0.64). Results in the intent-to-treat and second-line populations were generally consistent with previous analyses, the investigators reported. No new adverse events were seen.

“It is a tremendous achievement to see such remarkable, consistent overall survival results from the MONALEESA clinical trial program, demonstrating how Novartis is transforming care for people with breast cancer as we continue to work toward cures,” said Jeff Legos, executive vice president, global head of oncology & hematology development. “The unique profile of Kisqali continues to be reinforced, with results from MONALEESA-3 pushing the boundaries of how using a Kisqali-combination treatment regimen can extend lives of postmenopausal women living with HR+/HER2– advanced breast cancer without compromising quality of life.”

Reference

Neven P, Fasching PA, Chia S, et al. Updated overall survival (OS) results from the first-line (1L) population in the phase III MONALEESA-3 trial of postmenopausal patients with HR+/HER2- advanced breast cancer (ABC) treated with ribociclib (RIB) + fulvestrant (FUL). Presented at: European Society for Medical Oncology Breast Cancer Congress; May 2-5, 2022; Berlin, Germany. Accessed May 8, 2022. Abstract LBA-4.