Cutaneous toxicities occurring during palbociclib (CDK4/6 inhibitor) and endocrine therapy in patients with advanced breast cancer: a single-centre experience.

PURPOSE: Treatment with Palbociclib, a cyclin-dependent kinase 4/6 inhibitor, has demonstrated significantly improved progression-free survival in patients with hormone receptor-positive, HER2-negative, advanced breast cancer, when used in combination with letrozole or fulvestrant endocrine therapies. However, limited information exists on its cutaneous adverse effects (AE). Hence, we conducted a retrospective cohort study to investigate the prevalence and management of cutaneous AE during palbociclib and endocrine therapy. METHOD: We included 324 adult patients with advanced breast cancer who received palbociclib between March 2016 and August 2020 within a tertiary comprehensive cancer centre. Patient demographics, details of previous and concurrent treatments, as well as treatment-related cutaneous AE were recorded from electronic records. RESULTS: The incidence of treatment-related cutaneous AE was 14.2% (46 from a total of 324 patients). The most frequent cutaneous reactions included maculopapular rash (41%), asteatosis (37%), pruritus and urticaria (20%), and bullous dermatitis reactions (9%). We identified two patients with treatment-induced subacute cutaneous lupus erythematosus, one case of bullous pemphigoid, and a single erythema multiforme. Patients received an average of 9 cycles of treatment, completing an average of 6 cycles before developing cutaneous AE, which persisted for a median of 43 days. Only 15% (n = 7) of affected patients required temporary suspension, and 4% (n = 2) required discontinuation. The majority were managed with potent topical steroids, with oral corticosteroids being required in 3 patients, and one patient required hydroxychloroquine. CONCLUSION: Our study describes both the spectrum of cutaneous AE of palbociclib and endocrine therapy, and approaches to management. Prompt management may limit the negative impact on patients, facilitating beneficial continuation of palbociclib and endocrine therapy.