Formal discussant Mafalda Oliveira, MD, PhD, of Vall d’Hebron Institute of Oncology in Barcelona, commented that monarcHER was a “well-designed, hypothesis-generating trial that addresses clinically relevant questions,” including whether cyclin-dependent kinase 4 and 6 inhibition now has broader application in the treatment of advanced breast cancer. She noted that in contrast to most other trials of anti-HER2 agents as third-line treatment and beyond, the monarcHER population was heavily pretreated, with more than half the patients having received more than three lines of prior treatment.
Although monarcHER was a “statistically positive trial,” Dr. Oliveira said there are some unanswered questions:
- Can the progression-free survival results be further improved, for example, by using additional biomarkers beyond estrogen receptor positivity to better select the treatment population?
- What are the data in patients with central nervous system disease?
- What were the rates and duration of grade 2 diarrhea, and did this side effect impact quality of life?
- How often were dose reductions needed in response to treatment-emergent adverse events?
These questions aside, Dr. Oliveira concluded, “Abemaciclib plus trastuzumab plus endocrine therapy may be a valid strategy for treating estrogen receptor–positive, HER2-positive metastatic breast cancer.”
DISCLOSURE: Dr. Oliveira reported support from or other relevant relationships with AstraZeneca, Philips Healthcare, Genentech, Roche, Novartis, Immunomedics, Seattle Genetics, GlaxoSmithKline, Boehringer Ingelheim, Puma Biotechnology, Roche, Pierre-Fabre, GP Pharma, and Grünenthal.
