Abstract PO2-20-07: A case report of a severe cutaneous adverse event in triple negative breast cancer treated with chemoimmunotherapy
Authors: Zhang Annie , Beveridge Mara , Moftakhar Bahar 
Published: May 2024

Abstract
Introduction Cutaneous adverse events related to immune checkpoint inhibitors (ICI) are common and most are mild. However, numerous case reports have documented severe ICI-related skin-toxicities such as Stevens-Johnsons Syndrome (SJS) most commonly among patients with melanoma and lung cancer as immunotherapy has now become a mainstay of treatment in these tumors. The use of ICIs in breast cancer treatment has only recently become standard of care for treatment of metastatic and high risk early-stage triple negative breast cancer with the publication of two landmark clinical trials, KEYNOTE-355 and KEYNOTE-522, respectively. While these trials report low rates of severe skin reactions, little is known about ICI-related severe skin toxicities in patients with breast cancer.
Case description A 58-year-old female with clinical stage IIB (cT2N0M0) triple negative breast cancer was undergoing neoadjuvant treatment with pembrolizumab, an anti-programmed death (PD-1) monoclonal antibody, coupled with a chemotherapy back-bone of 12 weekly treatments of carboplatin and paclitaxel followed by 4 cycles of doxorubicin and cyclophosphamide. She developed an erythematous and itchy rash on the right breast and axilla approximately 61 days into her treatment course after having received her fourth dose of pembrolizumab. Over the next 10 days, she developed progression of the rash with painful red papules coalescing into reticulated plaques and dusky blistering of the skin involving the right arm, axilla, abdomen, inguinal folds, thigh, and back, totaling &lt; 10% total body surface area. Notably, the rash did not have mucosal involvement. She was hospitalized for close monitoring and treatment.
A punch biopsy of the rash revealed interface dermatitis with areas of full thickness skin necrosis consistent with erythema multiforme, SJS, toxic epidermal necrolysis (TEN), or a fixed drug eruption. Her skin continued to slough in the distribution of rash and a diagnosis of SJS was made. The patient had no response to initial treatment with high dose steroids. Cyclosporine was added, resulting in rapid improvement of her rash.
The patient’s neoadjuvant treatment was stopped given the grade 3 SJS she experienced. Despite this truncated neoadjuvant treatment, she had excellent clinical response as her tumor was no longer palpable. She proceeded with a partial mastectomy and sentinel lymph node biopsy. Pathology revealed a pathological complete response. She did not receive any further systemic therapy in the adjuvant setting. Three months later, she was evaluated in clinic without evidence of SJS on physical exam. She was rapidly tapered off cyclosporine over one week without recurrence of her rash.
Discussion Severe cutaneous adverse events related to ICIs remains an emerging area of study. In SJS, drug-specific CD8+ T lymphocytes utilize granulysin to mediate keratinocyte apoptosis. It is hypothesized that the blocking of the PD-1/PD-L1 interaction by ICIs results in the disruption of T-cell homeostasis leading to self-directed cytotoxic and inflammatory reactions and ultimately epidermal detachment. In contrast, Molina et al 2020 postulate that such ICI-related skin reactions may represent a separate clinical entity from SJS. In their case report of seven patients, they propose the term “progressive immunotherapy-related mucocutaneous eruption” (PIRME), which the authors suggest is characterized by delayed symptom onset, mild initial presentation, rare ocular involvement, benign clinical course, and favorable treatment response. Further characterization of ICI-related cutaneous adverse events is needed to understand the disease course, optimal treatment, and importantly, implications for re-challenging patients with immunotherapy. Clinicians taking care of breast cancer patients treated with ICIs need to be educated to recognize the associated skin toxicities as patients can rapidly worsen without appropriate treatment.
Citation Format: Annie Zhang, Mara Beveridge, Bahar Moftakhar. A case report of a severe cutaneous adverse event in triple negative breast cancer treated with chemoimmunotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-20-07.