Ribociclib regimen may be superior to chemotherapy in advanced breast cancer
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SAN ANTONIO — First-line ribociclib plus endocrine therapy appeared associated with longer PFS and fewer adverse events than combination chemotherapy among certain patients with advanced breast cancer, according to study results.
The findings of the phase 2 RIGHT Choice trial — presented at San Antonio Breast Cancer Symposium — showed the combination benefitted pre- or perimenopausal patients with hormone receptor-positive, HER2-negative disease, even if they had visceral crises.
The more durable efficacy benefit and improved tolerability may result in “an evolution of our standard of care” for patients with difficult-to-treat breast cancer, according to researcher Yen-Shen Lu, MD, PhD, professor at National Taiwan University Hospital.
“These findings suggest that, through the use of first-line ribociclib plus endocrine therapy, we may be able to avoid or delay chemotherapy and spare patients — even those with aggressive, life-threatening disease — the toxicities and discontinuations associated with chemotherapy,” Lu said in a press release.
Chemotherapy is the preferred initial treatment for patients with aggressive hormone receptor-positive, HER2-negative advanced breast cancer, including those with visceral crisis.
However, the combination of the cyclin-dependent kinase (CDK) 4/6 inhibitor ribociclib (Kisqali, Novartis) plus endocrine therapy has been associated with longer survival and better quality of life in this patient population, according to study background.
In RIGHT Choice, Lu and colleagues assessed outcomes of patients with aggressive breast cancer treated with ribociclib plus endocrine therapy vs. those who received combination chemotherapy.
The analysis included 222premenopausal or perimenopausal patients with hormone receptor-positive, HER2-negative aggressive breast cancer, more than half of whom had investigator-determined visceral crises.
Researchers randomly assigned 112 patients to ribociclib (600 mg on a 3-weeks-on, 1-week-off schedule) plus an aromatase inhibitor — either letrozole or anastrozole — and goserelin. The other 110 patients received physician’s choice of combination chemotherapy.
PFS served as the primary endpoint.
Researchers reported longer median PFS (24 months vs. 12.3 months; HR = 0.54; 95% CI, 0.36-0.79) and longer median time to treatment failure (18.6 months vs. 8.5 months) among patients assigned ribociclib plus endocrine therapy. Overall response rate appeared comparable between the ribociclib and chemotherapy groups (65.2% vs. 60%).
A lower percentage of patients assigned ribociclib plus endocrine therapy experienced any serious treatment-related adverse event (1.8% vs. 8%) or grade 3/grade 4 serious treatment-related adverse events (0.9% vs. 7%).
Fewer patients assigned ribociclib plus endocrine therapy had to discontinue at least one component of study treatment due to adverse events (7.1% vs. 23%).
“To be able to extend lives, treatment compliance is key,” Lu said. “A treatment with improved tolerability will definitely enhance compliance and, thus, increase the chances of longer disease control.”
Investigators hope subgroup analyses will provide insights into which patients may derive the most benefit from ribociclib plus endocrine therapy vs. chemotherapy.
Researchers acknowledged study limitations, including its small sample size and the inability to generalize the findings beyond the first-line treatment setting.
“The results of the RIGHT Choice study reveal that initial ribociclib plus endocrine therapy can be an efficacious, clinically meaningful treatment option for patients with aggressive advanced breast cancer and may help avoid the need for chemotherapy and its associated toxicities,” Lu said during a presentation.
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Lu Y-S, et al. Abstract GS1-10. Presented at: San Antonio Breast Cancer Symposium; Dec. 6-10, 2022; San Antonio.
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