Endocrine therapy remains a mainstay in the treatment of early-stage hormone receptor-positive breast cancer. However, oncologists continue to work on improving the risk of recurrence in patients whose tumors exhibit high-risk features, such as a larger size or lymph node involvement.
The MonarchE trial, a randomized phase 3 trial in adults, examined how the addition of abemaciclib to standard endocrine therapy could improve outcomes in high-risk early stage hormone receptor-positive breast cancer. Abemaciclib is an oral medication that is already used in metastatic hormone receptor-positive breast cancer but is new to the space of early-stage breast cancer. In contrast to standard endocrine therapy, abemaciclib targets estrogen-based signaling pathways that allow cancer growth and proliferation.
The investigators found that the addition of abemaciclib to standard endocrine therapy in these higher-risk patients improved how long patients remained disease free and alive (an absolute difference of 6.4% – 79.4% in the endocrine therapy alone group, and 85.8% in the abemaciclib + endocrine therapy group). Given how frequently breast cancer impacts our communities, this difference is significant and an exciting improvement and option for our patients.
With any addition of therapy, it is imperative to consider potential side effects. Patients who received both endocrine therapy and abemaciclib had higher rates of neutropenia and diarrhea, although most of these side effects were manageable with proper supportive care and monitoring. Like anything else, these side effects are something we discuss and need to personalize for each patient. In addition to abemaciclib, many similar class drugs are being examined (such as ribociclib) in this setting, further improving the options available to our patients.
