Advantage of Abemaciclib Plus Endocrine Therapy for Early Breast Cancer Endures at 5 Years

Findings Confirm Value of Combined Treatment

“It was reassuring to see the continued benefit at 5 years with adjuvant abemaciclib in combination with endocrine therapy compared to endocrine therapy alone in this high-risk HR+, HER2– EBC [early breast cancer] population,” Manali Ajay Bhave, MD, a medical oncologist at Emory University, Atlanta, said in an interview.

“While the interim overall survival analysis was not significant, further follow-up is necessary to truly discern a survival benefit particularly in this patient population where a survival advantage may not be seen for several years,” she added.

The current study supports the continued use of adjuvant abemaciclib in high-risk HR+, HER2– EBC patients, Dr. Bhave said. “Investigation of novel endocrine agents in the adjuvant setting for patients with high risk, HR+ HER2– EBC is needed to further improve outcomes.”
 

Urgent Need to Improve Adjuvant Therapy

“The monarchE study is a timely study aimed at improving adjuvant treatments in ER+ breast cancer to reduce risk of late recurrences,” Malinda T. West, MD, of the University of Wisconsin, said in an interview. “Late recurrences occurring decades later is a risk associated with ER+ breast cancer, and the risk of breast cancer recurrence is highest in those with larger tumors and nodal involvement.

“Abemaciclib is one of the three FDA-approved cyclin-dependent kinase 4/6 inhibitors in metastatic ER+ breast cancer based on demonstrated efficacy and safety in the metastatic setting compared to endocrine therapy alone, which was the rationale for expanded use of abemaciclib into the adjuvant setting for those at high risk for recurrence and basis of the monarchE trial,” said Dr. West.

An important criterion for inclusion was the randomization to abemaciclib required within 16 months of definitive breast cancer surgery, which reflected a window of time in which to start adjuvant abemaciclib, Dr. West said. “Exclusion criteria were those with a history of thromboembolic events, as abemaciclib carries a warning for venous thromboembolism,” she added.

In the monarchE follow-up, Dr. West said she was encouraged by the persistent and widening benefit with 2 years of added abemaciclib to endocrine therapy in reducing IDFS and DRFS compared to endocrine therapy alone.

Dr. West advised clinicians to consider initiating the therapy for up to 16 months after definitive breast surgery, because doing so may allow for recovery from surgery, chemotherapy, and radiation.

The findings tell physicians to “use caution with adding abemaciclib in those with a history of thromboembolic events or VTE risk factors as abemaciclib has a known VTE warning and this population was excluded in the monarchE trial,” she noted.

“Continued long-term follow up of those in this study will be important to determine survival benefits and how the predictive biomarker Ki-67 may impact survival outcomes,” she said.

The study was supported by Eli Lilly. Lead author Dr. Rastogi disclosed travel, accommodations, and expenses from Genentech/Roche, Lilly, and AstraZeneca. Several coauthors disclosed stock or ownership interests and/or other relationships with Lilly and other pharmaceutical companies. Dr. Goetz receives research funding from the National Institutes of Health. Dr. Bhave and Dr. West had no financial conflicts to disclose.