Overall survival with adjuvant ribociclib plus nonsteroidal aromatase inhibitor in patients with high-risk HR+/HER2- early breast cancer: Six-year follow-up of the NATALEE trial.

BACKGROUND

Ribociclib plus nonsteroidal aromatase inhibitor (NSAI) demonstrated a statistically significant invasive disease-free survival (iDFS) benefit over NSAI alone in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) early breast cancer (EBC) at the primary efficacy analysis of the phase 3 NATALEE trial. This prespecified 6-year analysis assessed overall survival (OS) and other efficacy outcomes as well as safety.

PATIENTS AND

METHODS

Eligible patients were adults with HR+/HER2- EBC and anatomic stage IIA (N1 or N0 with high-risk factors), IIB, or III disease. Enrolled patients were randomized 1:1 to ribociclib 400 mg/day (3 weeks on/1 week off for 3 years) plus NSAI (letrozole 2.5 mg/day or anastrozole 1 mg/day for 5 years) or NSAI alone. Premenopausal women and men also received goserelin. The primary endpoint was iDFS, and secondary/exploratory endpoints included OS, distant disease-free survival (DDFS), and distant recurrence-free survival (DRFS).

RESULTS

With a median OS follow-up of 66.5 months, ribociclib plus NSAI demonstrated an OS benefit over NSAI alone (6-year ΔOS, 2.1%; HR, 0.809 [95% CI: 0.661-0.989]; nominal 1-sided P = .019), which was generally consistent across key subgroups. An increasing iDFS benefit with ribociclib plus NSAI was also observed (6-year ΔiDFS, 5.3%; HR, 0.741 [95% CI: 0.646-0.849]; nominal 1-sided P < .0001), which was also generally consistent across key subgroups. DDFS (HR, 0.744 [95% CI: 0.646-0.858]) and DRFS (HR, 0.738 [95% CI: 0.634-0.858]) results supported these findings. No new safety signals were observed.

CONCLUSIONS

This prespecified descriptive 6-year OS analysis demonstrated positive OS results with a clinically relevant benefit of ribociclib plus NSAI, consistent with the increasing reduction in recurrence risk. These results reinforce the benefit of ribociclib plus NSAI in the adjuvant setting across the broad NATALEE-eligible population.

CLINICAL TRIAL REGISTRATION: NCT03701334 (ClinicalTrials.gov).