Response of advanced cutaneous squamous cell carcinoma to immunotherapy: case report.

The most common cancer in the United States is non-melanoma skin cancer. Cutaneous squamous cell carcinoma (cSCC) is the second most common non-melanoma skin cancer after basal cell carcinoma. It develops in the middle and outer layers of the skin. Its precursor is actinic keratosis, which can progress to squamous cell carcinoma in situ, invasive cSCC, and finally metastatic cSCC. About 20% of non-melanoma skin cancers are squamous cell and the remaining 80% are basal cell. Unlike basal cell, squamous cell carcinoma has the propensity to metastasize. This commonly occurs with squamous cell carcinoma (SCC) thicker than 2 millimeters. The risk of metastasis and local recurrence increases with 6 mm thickness and desmoplasia. The risk factors are excessive sun or ultraviolet light (tanning beds) exposure, immunosuppression (either having a weakened immune system or taking immunosuppressive therapy) and fair skin. Therefore, it most commonly affects skin in the head and neck area such as scalp, ears, lips, face, neck or the back of the hands. The treatment for local cutaneous squamous cell cancer is mainly surgery; excisional surgery, Moh's surgery, cryosurgery, curettage and electrodessication, laser surgery or radiation therapy, photodynamic therapy or topical agents such as fluorouracil or imiquimod. However, cSCC that is locally advanced, such as involvement of regional lymph nodes, or has metastasized to distant organs or tissue, is not amenable to surgery or radiation alone. Immunotherapy with cemiplimab, a programmed cell death 1 (PD-1) inhibitor, is a US Food and Drug Administration (FDA) approved therapeutic option for locally advanced and metastatic cSCC for patients who are not candidates for or whose disease is not susceptible to curative surgery or radiation therapy. Cemiplimab is a humanized recombinant immunoglobulin monoclonal antibody that binds to and blocks PD-1 receptor found on T cells inhibiting T-cell proliferation and cytokine production. We present a case of locally advanced cSCC with regional lymph nodes metastases, which achieved clinical remission, utilizing a unique approach of therapy combining a checkpoint inhibitor, Cemiplimab and radiotherapy.