Novartis said Kisqali (ribociclib) plus endocrine therapy was associated with a 19.1% lower risk of death in a six-year analysis of NATALEE, which studied high-risk stage II and III HR-positive, HER2-negative early breast cancer.
The company reported an overall-survival hazard ratio of 0.809, with a 95% confidence interval of 0.661 to 0.989. It put the absolute overall-survival difference at 2.1 percentage points at year six, up from 1.2% at year five.
NATALEE randomized 5,101 adults across 20 countries. The population included high-risk stage II and III HR-positive, HER2-negative patients, among them high-risk node-negative patients and node-positive patients in that same eligible group. Participants in one arm received ribociclib plus anastrozole or letrozole, with goserelin where applicable; the comparison arm received the aromatase inhibitor alone, also with goserelin where applicable.
Invasive disease-free survival was the trial’s primary endpoint. At six years, Novartis reported a 5.3-percentage-point absolute benefit for that measure, with a hazard ratio of 0.741 (95% confidence interval, 0.646-0.849). It also reported six-year absolute benefits of 4.9% for distant disease-free survival and 4.4% for distant recurrence-free survival.
The earlier peer-reviewed analysis at five years reported an overall-survival hazard ratio of 0.800 (95% confidence interval, 0.637-1.003) and characterized the finding as a positive numerical trend. At the six-year analysis, patients had been off Kisqali for a median of 38 months, Novartis said; they also had passed the protocol-specified five-year endocrine-therapy period.
Dennis J. Slamon, chief of the Division of Hematology/Oncology at UCLA Department of Medicine, called the results a “clinically meaningful improvement in overall survival.”
Novartis said no new safety signals emerged during extended follow-up. Secondary primary malignancies were reported in 3.0% of patients receiving the combination and 3.3% in the endocrine-therapy-only group. Fatal cases were 0.2% in each group. Novartis cited the 2026 ESMO Congress as the setting for its six-year data presentation.
