According to 4-year landmark analysis results from the phase 3 NATALEE trial, ribociclib added to nonsteroidal aromatase inhibitor (NSAI) treatment decreased the risk of invasive and distant disease recurrence by 28.5% among patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, compared with treatment with NSAI alone. This benefit persisted after 3 years of scheduled treatment, demonstrating an absolute benefit of up to 4 years. 

These results were first presented by Peter Fasching, MD, Comprehensive Cancer Center Erlangen-EMN, Erlangen, Germany, at the 2024 European Society for Medical Oncology (ESMO) Congress in Barcelona, Spain. 

In this study, patients with stage IIA, IIB, or III HR-positive, HER2-negative breast cancer were randomized on a 1-to-1 basis to receive either 2.5 mg of letrozole or 1 mg of anastrozole (for a duration of 5 years) alone or in combination with 400 mg of ribociclib (administered every third week with 1 week off for a duration of 3 years). Men and premenopausal women received goserelin in addition. The primary end point was invasive disease-free survival (iDFS) rate. Secondary end points included distant disease-free survival (DDFS) rate and overall survival (OS). 

At a median follow-up of 44.2 months, the 3-year iDFS rate was 88.1% in the NSAI arm and 90.8% in the ribociclib arm (hazard ratio [HR], 0.715; 95% confidence interval [CI], 0.609 to 0.840; P < .0001) and 4-year iDFS rate was 83.6% in the NSAI arm and 88.5% in the ribociclib arm, with an absolute improvement of 4.9% and 2.7%, respectively. The HR for DDFS benefit with ribociclib was 0.715. The OS results were immature at the time of analysis but trended in favor of ribociclib (HR 0.827; 95% CI, 0.636 to 1.074). Safety was consistent with prior results. 

As Dr Fasching et al concluded, “these results further support the addition of ribociclib to adjuvant NSAI in a broad population of [patients with HR-positive/HER2-negative early breast cancer] at risk of recurrence.” 

Source: 

Fasching PA, Stroyakovskiy D, Yardley D, et al. Adjuvant ribociclib (RIB) plus nonsteroidal aromatase inhibitor (NSAI) in patients (Pts) with HR+/HER2− early breast cancer (EBC): 4-year outcomes from the NATALEE trial. Presented at 2024 ESMO Congress. September 13-17, 2024. Abstract LBA13