Palbociclib-Induced Subacute Cutaneous Lupus

Targeted therapies offer new alternatives to chemotherapy by sparing healthy tissue and concentrating on cancer cells. In this way, they can break the therapeutic deadlock for some patients. Three CDK 4/6 inhibitors - palbociclib, ribociclib and abemaciclib - are used in a variety of oncological indications and are currently part of the reference treatment for ER-positive and HER2-negative metastatic breast cancer. Cutaneous toxicity has been described with these three compounds, with no improvement in skin lesions after changing the compounds, suggesting a class effect. A 54-year-old woman treated for metastatic breast cancer at the Mohammed VI Cancer Treatment Centre, Ibn Rochd Hospital, between January 2023 and the present day. She was admitted to the department in January 2024 with a photo-distributed skin rash that appeared approximately six weeks after the start of her treatment with palbociclib and letrozole. Skin biopsy was consistent with interface dermatitis with vacuolisation and thickening of the basement membrane, a discrete superficial dermal inflammatory infiltrate, epidermal atrophy and fine mucinous deposits. All the clinical, histological and biological features were compatible with subacute cutaneous lupus. Palbociclib was discontinued and the rash began to clear spontaneously. The most common side effects with these three compounds (palbociclib, ribociclib and abemaciclib) are alopecia, pruritus and maculopapular rash. Other rarer cutaneous side effects have been described, such as erythema multiforme, bullous pemphigoid and subacute cutaneous lupus. As the use of CDK 4/6 inhibitors increases, this skin toxicity must be recognised in order to treat it effectively and facilitate the continuation of oncology treatment.