Unresectable advanced cutaneous squamous cell carcinoma: Patient characteristics and outcomes following anti PD-1 treatment from a single institution.

Abstract

e21545 Background: Patients (pts) with unresectable advanced cutaneous squamous cell carcinoma (UACSCC) have favorable outcomes following FDA approved anti PD-1 therapy. High tumor mutation burden and host comorbidities and immune defects underlie patient and disease characteristics. We report our results following anti PD-1 treatment of UACSCC pts. reflecting the real-world experience in this population. Methods: We retrospectively analyzed case records of patients treated for UACSCC from 2016 to 2024 with anti PD-1 treatment. Patients were eligible if at least one cycle of anti PD-1 therapy was administered. We reviewed patient characteristics such as age, gender, comorbidities, treatment as well as toxicities and outcomes. Results: 26 pts were eligible for analysis. 20 males, six females (M:F 20:6). The median age is 79 years (yrs.) (range 60-102 yrs). Primary tumor sites included Head and neck, Extremities and Trunk in 17, 4 and 5 pts respectively. Pts. received a median of 12 cycles of anti PD-1 agent (range 1-102+ doses). 24 and 2 pts received Cemiplimab and Pembrolizumab respectively. In 1 pt Nivolumab replaced Cemiplimab after 3 cycles due to infusion reaction. 21 out of 26 pts responded to treatment (response rate RR) 80.77%, while 5 pts (19.23%) had refractory disease (RD). Of the 21 responses, there were 17 complete responses (CR), (80.95%) and 4 partial responses (PR) 19.05%. Durable responses were observed in all three primary tumor sites. The median survival of all pts is 13 months (mths) (range 1-78 +mths) and of responding pts 17 mths (4-78+ mths) and of those in CR is 17 mths (4-78+ mths).18 pts are alive of which 15 are in CR, one has ongoing response, one has recurrent disease, one refractory disease (RD). 1pt is lost to follow up. 7 pts died, 4 with RD and 1 PR. 1 pt with RD developed grade II pneumonitis and died on hospice. 1 pt with PR died of grade IV pneumonitis. 2pts died in CR of unrelated causes; 1 pt had subarachnoid hemorrhage from Arterio-Venous malformation and 1 pt of advanced age died of urinary sepsis. Of 5 RD pts, one had severe dementia, 1 had steroid dependent COPD, 1 had severe psoriasis receiving biologic therapy, and 2 pts with comorbidities were of advanced age (96 and 102 yrs). Of 4 pts with PR, 1pt had severe COPD/tobacco use, 1pt. COPD/mild dementia, 1pt. has advanced basal cell carcinoma. 1 pt on active treatment has ongoing response. Conclusions: Anti PD-1 treatment of UACSCC in the real-world result in high response rates that are durable and higher than those reported in selected fit patients treated in clinical trials. Careful monitoring of immune related adverse events is required in this patient population some of who have impaired communication and social support.