Posted: Tuesday, December 13, 2022
Stephen Johnston, MBBS, of The Royal Marsden Hospital, London, United Kingdom, and colleagues conducted a study that combined adjuvant abemaciclib with endocrine therapy in patients with hormone receptor–positive, HER2-negative, early-stage breast cancer. The 4-year overall survival analysis with the combination of this CDK4/6 inhibitor and hormonal therapy was presented during the 2022 San Antonio Breast Cancer Symposium (SABCS; Abstract GS1-09).
“The clinically meaningful benefit of adjuvant abemaciclib added to endocrine therapy in [this] cancer persists beyond completion of abemaciclib therapy, yielding an increase in absolute invasive disease–free survival and distant relapse–free survival benefit at 4 years,” concluded the investigators. “While overall survival remains immature at this time, the lower number of deaths in the abemaciclib arm compared to the endocrine therapy arm suggest that a survival signal favoring abemaciclib is emerging.”
A total of 5,637 patients with hormone receptor–positive, HER2-negative, node-positive, early-stage breast cancer were enrolled. Participants were randomly assigned on a 1:1 basis to receive endocrine therapy for up to 10 years with or without abemaciclib for 2 years.
All patients had ceased receiving abemaciclib at the median follow-up of 42 months. The hazard ratios were 0.664 for invasive disease–free survival and 0.659 for distant relapse–free survival. Additionally, there was an observed improvement in both invasive disease–free survival (79.4% to 85.8%) and distant relapse–free survival (82.5% to 88.4%) rates at 4 years.
A lower number of deaths observed with the combination therapy versus endocrine therapy alone (157 vs. 173) suggests the benefit in invasive disease–free survival and distant relapse–free survival may translate into a numerically favorable overall survival hazard ratio. In addition, a Ki67 index of at least 20% was associated with a worse prognosis among patients with positive axillary lymph nodes or who had grade 3 disease. No new safety signals were observed.
Disclosure: For full disclosures of the study authors, visit sabcs.org.