Dr Bardia on Results of the NATALEE Trial in HR+/HER2– Early Breast Cancer

Aditya Bardia, MD, MPH, attending physician, medical oncology, Massachusetts General Hospital, director, breast cancer research, Mass General Cancer Center, associate professor, medicine, Harvard Medical School, discusses the investigation of ribociclib (Kisqali) and endocrine therapy vs endocrine therapy alone as adjuvant treatment in patients with hormone receptor (HR)–positive/HER2-negative early breast cancer, highlighting primary results from the phase 3 NATALEE trial (NCT03701334).

Overall, the NATALEE trial showed positive results, meeting the study’s primary end point and demonstrating that patients who received endocrine therapy plus ribociclib had an improvement in invasive disease-free survival (iDFS) compared with endocrine therapy alone (HR, 0. 748; 95% CI, 0.618-0.906; P = .0014). Data presented at the 2023 ASCO Annual Meeting showed that the 3-year iDFS rate was 90.4% with ribociclib plus endocrine therapy vs 87.1% with endocrine therapy alone.

At the time of data cutoff, 57% of patients in the experimental arm were continuing treatment for at least 2 years, and 20% of patients completed 3 years of treatment with ribociclib. Further follow-up is required to better understand the long-term effect of the addition of ribociclib to endocrine therapy, Bardia says. Moreover, the trial showed a trend towards improvement in overall survival (OS), though there must be further follow-up to better understand if an OS benefit is observed in the experimental arm, Bardia says.

Enrolled patients were randomly assigned 1:1 and received ribociclib at 400 mg per day on a 3-weeks-on/1-week-off schedule plus endocrine therapy, or endocrine therapy alone. This dose of ribociclib was lower than the 600-mg dose typically used in the metastatic setting, Bardia explains. The overall safety profile aligned with the known toxicity profile for ribociclib, resulting in patients who presented with myelosuppression, neutropenia, and liver-related adverse effects. However, incidences of these were lower compared with what would have been expected with a dose of 600 mg, Bardia notes. Even at a 400 mg dose, Bardia concludes that there was still an improvement in iDFS.