Alopecia as an Adverse Event of Immune Checkpoint Inhibitor Therapies: Clinical Evidence and Outcomes

Immunotherapy utilizing immune checkpoint inhibitors (ICIs) such as PD-1, PD-L1, and CTLA-4 inhibitors has revolutionized cancer therapy by enhancing T cell recognition and attack against cancer cells.1 Immune-related adverse events (irAEs) are a limitation of ICI therapy, encompassing various manifestations such as colitis and cutaneous adverse events such as dermatitis, alopecia, and vitiligo.2 Hair loss is a common concern of cancer patients as they embark on their therapeutic paths. The evidence on alopecia from isolated clinical trials with ICI therapies is limited and largely lacks diagnostic and prognostic details to help guide patients.3,4 In this systematic review, we examined the types of alopecia as part of the irAEs of ICI therapy, timing of onset, prognosis, and treatment approaches. Our analysis includes 19 studies describing new-onset non-scarring or scarring alopecia following ICI treatment. Alopecia was a rare adverse event in the setting of ICIs (n=26) with the onset of alopecia occurring within one year of initiating treatment. Slightly over half of the affected patients reported some degree of hair regrowth after attempted alopecia-directed treatments. We discuss available data to increase awareness of this rare but potentially permanent side effect of ICI therapy. Further research is warranted to enhance our understanding of alopecia as an irAE and to optimize patient management strategies. J Drugs Dermatol. 2025;24(3):255-260. doi:10.36849/JDD.7828.