A MONALEESA-7 subgroup analysis of Asian patients with HR+/HER2- advanced breast cancer found that those treated with ribociclib and a non-steroidal aromatase inhibitor (NSAI) lived significantly longer overall than patients who received an NSAI alone, according to findings presented at the ESMO Asia Virtual Congress 2020 (Abstract 47MO).
The researchers reported that the combination of ribociclib and an NSAI improved progression-free survival almost three-fold compared to placebo plus NSAI. This analysis also showed that treatment with ribociclib and a NSAI improved overall survival with a 56 percent relative reduction in the risk of death.
"The Phase III MONALEESA-7 trial demonstrated efficacy, safety, and improvement in quality of life of pre- and perimenopausal patients with HR+/HER2- advanced breast cancer treated with ribociclib or placebo plus endocrine therapy," noted study author Yen-Shen Lu, MD, Chief of Medical Oncology in the Department of Medical Oncology at the National Taiwan University Hospital, Taipei.
A significant overall survival benefit was observed for ribociclib plus endocrine therapy compared to placebo, according to Lu. Findings from the MONALEESA-7 trial also demonstrated an overall survival benefit among the NSAI subgroup for ribociclib versus placebo that was consistent with the overall population.
The MONALEESA-7 study included pre- and perimenopausal patients with HR+/HER2- advanced breast cancer. Eligible patients included patients who had not been previously treated with endocrine therapy for advanced breast cancer.
Patients were randomized (1:1) to receive ribociclib plus endocrine therapy (NSAI or tamoxifen) or placebo plus endocrine therapy. The primary endpoint was progression-free survival. Secondary endpoints included overall survival, objective response rate, clinical benefit rate, quality of life, and safety.
Subgroup Findings
This prespecified subgroup analysis included 166 Asian patients (34% of the total NSAI cohort) in Asia, Europe, Australia, North America, and other countries. Eighty-two were treated with ribociclib and 84 received placebo.
Among Asian patients in the ribociclib plus NSAI arm, 26 (31.7%) had de novo metastatic disease, and 3.7 percent and 64.6 percent had a disease-free interval of <= 12 months and >12 months, respectively.
The objective of this analysis was to evaluate the efficacy, safety, and quality of life of these patients in the MONALEESA-7 trial receiving ribociclib plus NSAI or placebo plus NSAI.
"The baseline patient characteristics were well balanced between the two arms and, in comparison, to the overall NSAI population," explained Lu. "At the Nov. 30, 2018, data cut-off, 33 patients in the ribociclib arm and 16 patients in the placebo arm were still receiving standard treatment. The primary reason for discontinuation in both the Asian and the overall NSAI populations was disease progression."
The median progression-free survival was 30.4 months in the ribociclib arm compared with 11.0 months in the placebo arm, according to Lu. "The improvement in progression-free survival observed for the Asian population was consistent with the overall NSAI population," he said. "The overall survival in both arms was not reached at the data cut off."
The Kaplan-Meier estimated overall survival at 36 months was 78.9 percent in the ribociclib arm and 61.5 percent in the placebo group, according to Lu, who noted that "the improvement in overall survival benefit observed for the Asian [cohort] was consistent with the overall NSAI population."
Both overall response rate and clinical benefit rate improved significantly with the combination of ribociclib and NSAI. Lu reported a chemotherapy-free survival of 58 percent and a 50 percent reduction in the risk of progression on second-line therapy in patients treated with ribociclib plus NSAI.
"Compliance rates for taking the EORTC QLQ-C30 questionnaire were at least 94 percent through cycle 40," Lu said. "The Global Health score was generally maintained during ribociclib treatment. No formal statistical comparisons were performed on time to deterioration due to low patient numbers."
Adverse events in the Asian subgroup were consistent with the overall population, according to Lu. Neutropenia was the only grade 3/4 adverse event observed in either arm.
"Efficacy, quality of life, and safety in Asian subgroup of MONALEESA-7 were consistent with the overall NSAI population," Lu concluded. "Ribociclib improved median progression-free survival almost three-fold. The relative risk of death was reduced 56 percent with ribociclib. Quality of life was maintained with ribociclib treatment."
Catlin Nalley is a contributing writer.