Cyclin-Dependent Kinase 4/6 Inhibitors and Dermatologic Adverse Events: Results from the EADV Task Force "Dermatology for Cancer Patients" International Study

BACKGROUND

The introduction of cyclin-dependent kinase inhibitors (CDK4/6i) was a great advance in therapeutics for patients with estrogen receptor+/human epidermal growth factor receptor (HER2) locally advanced and metastatic breast cancer. Despite the increasing use of these agents, their adverse drug-related events have not yet been fully characterized. We describe the spectrum of cutaneous adverse reactions occurring in advanced breast cancer patients treated with cyclin-dependent kinase inhibitors, analyzing types, severity, time to onset, and possible treatment outcomes.

METHODS

We performed a multicentric retrospective study including patients with advanced breast cancer who developed cutaneous lesions during treatment with CDK4/6i in the period from June 2020 to June 2021. Patients > 18 years were recruited at eleven onco-dermatology units located in Albania (1), Argentina (1), France (1), Greece (3), Italy (3), and Spain (2). We evaluated patients' epidemiological and clinical characteristics, types of cutaneous adverse events, their time to onset, and treatment outcomes. The severity of the skin reactions was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 score.

RESULTS

Seventy-nine patients (median age: 62.3 years; range 39-83 years) were included in the study, and, collectively, we recorded a total of 165 cutaneous adverse events during follow-up visits. The most frequent cutaneous reactions were pruritus (49/79 patients), alopecia (25/79), and eczematous lesions (24/79). Cutaneous toxicities were usually mild in severity (>65%) and occurred after a median of 6.5 months. Only four patients (5%) required treatment discontinuation due to the severity of the skin lesions. The majority of the skin reactions were managed with topical treatments.

CONCLUSIONS

To the best of our knowledge, we present the largest case series of cutaneous adverse events developing in advanced breast cancer patients treated with CDK4/6i. We showed that cutaneous toxicities are usually mild in severity, and manageable with standard supportive care; however, in selected cases, they can lead to treatment discontinuation with possible implications for patients' clinical outcomes.

Case report: Vitiligo-like toxicity due to ribociclib during first-line treatment of metastatic breast cancer: two cases of premature interruption of therapy and exceptional response

Cancer treatment-related adverse events (AEs) are sometimes associated with outcomes for cancer patients, especially with the newest therapies such as target therapy and immunotherapy. A few years ago, the first-line therapy for hormone-receptor-positive metastatic breast cancer (mBC) patients has been deeply changed by the introduction of cyclin-dependent kinase (CDK) 4/6 inhibitors, and now, we are improving our knowledge about their AEs and significance in clinical practice. Here, we report our experience with two cases of vitiligo-like lesions that occur early during treatment with ribociclib. We tried to change the CDK4/6 inhibitor for one patient, but the skin reaction persisted. Both patients retained only the endocrine therapy alone and had an unexpected durable progression-free survival (PFS). Some data on skin toxicities, including vitiligo-like lesions by CDK4/6 inhibitors, have recently been reported in the literature, but for the first time, we highlight a possible correlation with improved survival outcomes of patients. Uncovering the etiology of this toxicity, verifying the involvement of the immune system, and demonstrating a possible positive impact in survival represent an intriguing research objective for the near future.