Abstract
BACKGROUND: Cutaneous squamous cell carcinoma (cSCC) is characterized by a high tumor mutational burden due to solar damage and a favorable response to anti-PD-1 immunotherapy. Yet, we encounter tumors arising in areas with minimal sun exposure, such as cSCC that develops in chronically inflamed skin, also known as Marjolin's Ulcer (MU). The response of MU-SCC to immunotherapy remains unknown. METHODS: We performed a retrospective analysis of patients diagnosed with cSCC and treated with cemiplimab or pembrolizumab in a single tertiary medical center. Patients lost to follow up were excluded. RESULTS: Of the 84 eligible patients, 9 (11%) had MU-SCC. Of these, 2 (22%) reached partial response (PR), and none reached complete response (CR). In contrast, of the 75 patients with solar damage-related cSCC, 40 had PR (53%), and 20 had CR (26%). The difference between the two subtypes was significant (P < .001). Interestingly, 3 patients with MU-SCC received a second-line chemo-immunotherapy and experienced a partial response that continued for 5 to 21 months. Patients with MU-SCC had a significantly shorter median time to progression (TTP) (1.6 vs 51.6 months, P < .001) and progression-free survival (PFS) (1.6 vs 15.4 months, P < .001). Overall survival (OS) was not significantly shorter (17.4 vs 36.7 months, P = .096). Multivariate analysis confirmed that MU-SCC is an independent risk factor for shorter TTP (HR 5.5, 95% CI 2.2-14.0, P < .001) and PFS (HR 3.5, 95% CI 1.5-8.1, P = .003). CONCLUSIONS: This study suggests that immunotherapy is less beneficial in SCC-MU. More work is needed to verify our findings and explore other treatment options.