Background and importance Cutaneous squamous cell carcinoma (CSCC) is the second most common skin cancer. Risk factors for CSCC include chronic sun exposure, advanced age, skin that is sensitive to ultraviolet radiation and immunosuppression. Patients who have undergone solid organ transplantation and are receiving immunosuppressive therapy have a high risk of CSCC, which suggests that immune surveillance is critical for preventing CSCC in immunocompetent people. Immune checkpoint inhibitors, such as the anti-PD1 monoclonal antibody cemiplimab, have proven efficacy as firstline therapy for the treatment of adult patients with metastatic or locally advanced CSCC, who are not candidates for curative surgery or radiation.

Aim and objectives We report a case of a patient with CSCC treated with cemiplimab.

Material and methods This was an observational retrospective study of the use of cemiplimab in a 66-year-old man diagnosed with CSCC. Data were obtained from the electronic medical records.

Results The patient was diagnosed with nose CSCC in May 2019 and had other comorbidities: B cell chronic lymphocytic leukaemia (B-CLL), hypothyroidism and atrial fibrillation. This CSCC was resected completely in June 2019, but a CT scan in December 2019 revealed minimal but progressive splenomegaly and supraclavicular lymphadenopathy and a posterior biopsy confirmed CSCC. Other abnormal adenopathies were observed (posterior cervical and axilla likely in relation to B-CLL). He started cemiplimab 350 mg every cycle (21 day cycles) on 6 February 2020. After six cycles, repeat CT scan showed an increase in the size of the supraclavicular adenopathy but it was decided to continue treatment for three more cycles to re-evaluate pseudo-progression versus disease progression. In cycle 9, a new CT scan revealed stability of disease and therefore the patient continued with his treatment. Regarding side effects, the patient had a grade 1 maculopapular rash related to the medication for 3 days.

Conclusion and relevance Immunotherapy, with its own pattern of response different from the pattern of conventional responses, makes the evaluation of the response complicated. In this case, we observed the effect of pseudo-progression followed by a response, complicating estimation of the real effect of cemiplimab, which was shown to be safe and effective, achieving stability of disease.

Conflict of interest No conflict of interest