Analysis of the Frequency and Associated Factors of Skin Toxicity in Patients Receiving Ribociclib-Based Therapy for Metastatic Breast Cancer

Abstract

Introduction: In the treatment of hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer (MBC), the current guidelines recommend endocrine therapy combined with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors as the preferred first-line treatment to preserve quality of life. Ribociclib is a CDK4/6 inhibitor that has been used in combination with aromatase inhibitors or fulvestrant in patients with HR+, HER2- metastatic breast cancer. Various adverse drug reactions associated with ribociclib have been reported, including cutaneous reactions, hepatotoxicity, and hematologic toxicity. In this study, we aimed to evaluate the clinical manifestations and risk factors of dermatologic toxicities in patients with metastatic breast cancer treated with ribociclib. Methods: This retrospective study included patients with metastatic/recurrent breast cancer who were prescribed ribociclib from April 2021 to December 2024 at a single institution. We retrospectively reviewed the medical records of these patients to identify the frequency of cutaneous adverse events, the time of onset, and the clinical characteristics of skin reactions. Logistic regression analysis was performed on several clinical factors, including body surface area (BSA) and concomitant medications, to identify risk factors associated with the occurrence of cutaneous adverse events. Results: A total of 110 patients with MBC were enrolled during the study period. The median age was 53 years (range, 28-82); all 110 patients (100.0%) were female; the median BSA was 1.56 m2 (range, 1.29-2.07); and 32 patients (29.1%) were premenopausal. Ribociclib plus letrozole was administered in 48 patients (43.6%) and ribociclib plus fulvestrant in 29 patients (26.4%). An additional 33 patients (30.0%) received ribociclib plus letrozole with a gonadotropin-releasing hormone (GnRH) agonist. Cutaneous adverse events occurred in 29 patients (26.4%), and the median time to onset was 84 days (range, 3-498). The cutaneous adverse event patterns included pruritus, erythematous macular rash, eczematous rash/contact dermatitis, vitiligo, urticarial reactions, polymorphous light eruption, toxic epidermal necrolysis (TEN), and desquamation. Grade 1 or 2 cutaneous adverse events occurred in 93.1% of patients; Grade 3 toxicity occurred in one patient; and Grade 4 toxicity, namely toxic epidermal necrolysis (TEN), was reported in one patient. Dose reduction was required in three patients (10.3%), and permanent discontinuation of ribociclib occurred in one patient. Clinical improvement was achieved in the majority of patients (86.2%) with cutaneous adverse events following supportive care. Logistic regression analysis revealed that age, Eastern Cooperative Oncology Group (ECOG) performance status, body surface area (BSA), treatment regimen, and use of cholesterol-lowering medications were not independently associated with the development of cutaneous adverse events. Conclusion: CDK4/6 inhibitors represent one of the most important treatment options for HR+/HER2- metastatic breast cancer. Regardless of their clinical efficacy, cutaneous adverse events remain a common source of patient discomfort. Therefore, careful clinical attention and appropriate supportive care are essential to improve patients' quality of life.