Pembrolizumab Induced Recall Dermatitis Occurring 5 Years After Radiotherapy

<b>Background and Clinical Significance:</b> Radiation recall dermatitis (RRD) following immune checkpoint inhibitor (ICI) therapy has been infrequently reported. <b>Case Presentation:</b> We present a 47-year-old female patient who developed RRD of the breast following three doses of pembrolizumab administered as an adjuvant treatment post-nephrectomy for Stage III renal cell carcinoma (RCC). Notably, the affected breast had previously undergone external beam radiotherapy 247 weeks earlier for Stage IA invasive ductal carcinoma. She had received no prior chemotherapy at any point. RRD manifested as breast induration, erythema, and peau d'orange, and contraction of breast volume was noted following three cycles of pembrolizumab on week 17 (400 mg dose every 6 weeks). The dermatitis responded rapidly to systemic corticosteroids and no treatment interruption was needed. <b>Conclusions:</b> To date, this is the longest reported interval from completion of radiotherapy to RRD. A literature search underscores the variability in presentation and management of ICI-associated RRD.