P019 Palbociclib-induced subacute cutaneous lupus erythematosus: a rare clinicopathological case

Abstract We describe a rare case of palbociclib-induced subacute cutaneous lupus erythematosus (DI-SCLE) in a patient with metastatic breast cancer. A 71-year-old woman had a history of ER/PR-positive, HER2-negative metastatic breast carcinoma on letrozole and palbociclib. She was prospectively evaluated after referral with a 5-month history of a progressive, pruritic, photodistributed rash. The patient developed an erythematous, papulosquamous eruption over the malar face, V of neck, arms, forearms and upper back after six cycles of palbociclib, with associated leucopenia and lymphopenia. Serology showed a speckled antinuclear antibody pattern with positive anti-Ro (SSA) and anti-La (SSB) antibodies and negative antihistone antibodies, and histology revealed interface dermatitis with perivascular inflammation (Russell-Goldman E, Nazarian RM. Subacute cutaneous lupus erythematosus with positive anti-Ro antibodies following palbociclib and letrozole treatment: a case report and literature review. J Cutan Pathol 2020; 47: 654–8). Direct immunofluorescence demonstrated fine granular IgM along the basement membrane and intraepidermal IgG antinuclear staining, favouring DI-SCLE. The rash persisted despite topical corticosteroids but resolved completely within 6 weeks of discontinuing palbociclib, while letrozole was continued, supporting a causal association. The patient subsequently re-presented with spinal cord compression due to progressive metastatic disease after stopping palbociclib. This case represents one of very few reported instances of palbociclib-induced DI-SCLE. This underscores the need for early recognition and management of cutaneous toxicity to enable continuation of life-prolonging oncological therapy where possible. A high index of suspicion should be kept for DI-SCLE in patients on CDK4/6 inhibitors presenting with new photodistributed eruptions, to prevent unnecessary treatment discontinuation and adverse ­cancer-related outcomes [Chawla S, Hill A, Fearfield L et al. Cutaneous toxicities occurring during palbociclib (CDK4/6 inhibitor) and endocrine therapy in patients with advanced breast cancer: a single-centre experience. Breast Cancer Res Treat 2021; 188: 535–45].