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Suspected Abscopal-Pattern Response following Radiotherapy in a Patient Receiving Cemiplimab for Advanced Cutaneous
William Earl Faunce1, Nicole Agostino2, Benjamin Foster3
1Lewis Katz School of Medicine at Temple University, Temple St. Luke's Campus, Bethlehem, PA, USA.
Introduction:
The abscopal effect is a rare phenomenon in which localized radiotherapy leads to regression of distant, nonirradiated tumors through systemic immune activation, often enhanced by immune checkpoint inhibitors. It is infrequently reported in cutaneous squamous cell carcinoma and even less so in immunocompromised patients. We report a case of head and neck cutaneous squamous cell carcinoma in an immunocompromised patient treated with PD-1 inhibition and localized radiotherapy, in which a distant untreated lesion regressed, consistent with a suspected abscopal response.
Case Presentation:
An 88-year-old immunocompromised male with a history of acute myeloid leukemia developed a biopsy-proven well-differentiated cutaneous squamous cell carcinoma of the head and a separate clinically suspicious scalp lesion concerning for malignancy. He was treated with systemic cemiplimab and subsequently received localized radiotherapy (30 Gy in 10 fractions) to a left postauricular lesion, while a separate left scalp lesion was outside the radiation field. Following completion of radiotherapy, the treated lesion demonstrated complete clinical response. Notably, the untreated scalp lesion also showed marked regression within weeks, consistent with an abscopal-pattern response. This occurred in the setting of chronic immunosuppression related to his underlying hematologic malignancy and its treatment.
Conclusion:
This case describes a suspected abscopal-pattern response in a patient with cutaneous squamous cell carcinoma receiving concurrent cemiplimab and localized radiotherapy. While regression of the untreated lesion following radiotherapy raises the possibility of a radiation-associated systemic immune response, the contribution of delayed PD-1 blockade response cannot be excluded. This case highlights the potential for systemic tumor regression during combined radiotherapy and immune checkpoint inhibition, including in an immunocompromised patient, while underscoring the need for further investigation into this interaction.
