Overall survival with adjuvant ribociclib plus NSAI in patients with high-risk HR+/HER2- early breast cancer: six-year follow-up of NATALEE

Primary analysis of the multinational phase 3 NATALEE trial found a significant invasive disease-free survival (iDFS) benefit with adjuvant ribociclib plus nonsteroidal aromatase inhibitor (NSAI) over NSAI alone in patients with HR-positive/HER2-negative (HR+/HER2-) early breast cancer (EBC). Six-year outcomes from NATALEE have now been reported. Eligible patients were adults with HR+/HER2- EBC and anatomic stage II or III disease. Enrolled patients (n=5101) were randomized 1:1 to ribociclib 400 mg/d (3 weeks on/1 week off for 3 years) plus NSAI (letrozole or anastrozole once daily for 5 years) or NSAI alone. Premenopausal women and men also received goserelin. The primary endpoint was iDFS. With a median follow-up of 66.5 months, an increasing iDFS benefit with ribociclib plus NSAI over NSAI alone was observed (6-year ΔiDFS 5.3%; HR 0.741; 95% CI 0.648-0.849) which was generally consistent across subgroups. Overall survival also was better with addition of ribociclib to NSAI (6-year ΔOS 2.1%; HR 0.809; 95% CI 0.661-0.989), which was also the case for distant disease-free survival (HR 0.744; 95% CI 0.646-0.858) and distant recurrence-free survival (HR 0.738; 95% CI 0.634-0.858). The authors conclude that this prespecified descriptive 6-year analysis demonstrated favorable outcomes with addition of ribociclib to NSAI among patients with high-risk HR+/HER2- EBC.