Retrospective cohort study of CDK4/6-inhibitor-induced alopecia in breast cancer patients

Purpose: Dermatologic adverse events commonly result in the interruption of oncologic treatment, and targeted therapies are the most frequently interrupted class of anticancer agents. Alopecia is a common cutaneous adverse event reported with CK4/6i therapy. Though the clinical characteristics and therapeutic response of EIA have been well documented, few studies have characterized alopecia in patients treated with CDK4/6i. Methods: This study analyzed a retrospective cohort of 28 breast cancer patients diagnosed with endocrine-induced alopecia (EIA) or CDKiA. Comparative analysis of the clinical characteristics of alopecia and therapeutic response to minoxidil was conducted. Therapeutic response to minoxidil (LDOM or topical [5%] solution or foam) was assessed by both Dean Scale and qualitative clinical improvement by comparison of pretreatment and posttreatment clinical images by single-blinded, board-certified academic dermatologists (ST and BD). Results: CDKiA was clinically similar to androgenetic alopecia and specific vertex involvement was more common in patients treated with CDK4/6i + ET than endocrine monotherapy (n = 7 [70.0%] vs n = 4 [36.4%]; p = 0.04), respectively. After 4–6 months of minoxidil, there was a moderate to significant qualitative alopecia improvement in 80% of CDKiA patients versus 94.4% of EIA patients. Additionally, superior improvement of mean Dean Score grade was observed in EIA (with change from pre- to posttreatment − 0.44; p = 0.0002). Conclusion: Compared to endocrine monotherapy, patients on combination CDK4/6i + ET had greater extent of vertex involvement and were more recalcitrant to minoxidil. The preferential vertex involvement observed in CDKiA suggests that combination therapy with minoxidil and topical antiandrogens with poor systemic absorption should be studied in this setting.