Intralesional Interleukin-2 Therapy for Treatment of Cutaneous Squamous Cell Carcinoma.

Abstract

Cutaneous squamous cell carcinoma (cSCC) remains one of the most common cancers affecting the general population. It is generally cleared surgically, yet it is challenging to manage recurrent disease, locally advanced disease, or disease in anatomically sensitive areas among patients, with few options available. To assess whether intralesional interleukin 2 (iIL-2) can effectively treat patients with high-risk or cosmetically sensitive cSCC. This case series took place at a single high-volume referral center for surgical oncology and intralesional immunotherapy for melanoma between 2017 and 2024. The center had considerable experience treating patients with locoregionally advanced melanoma using iIL-2, with high clinical efficacy and low treatment-related toxic effects. Patients referred to the immunotherapy program had histologically confirmed cSCC and failed prior surgical attempts or comorbidities that made them not candidates for surgery. Additionally, some patients had cSCC in cosmetically sensitive sites and were referred for a trial of intralesional immunotherapy prior to surgery. Intralesional IL-2 was administered biweekly at a concentration of 0.1 mL/2 mm2 to clinically positive lesions (500 000 IU/0.1 mL), and responses were recorded according to Immune Response Evaluation Criteria in Solid Tumors criteria. Injections were continued while patients responded and were stopped if any evidence of disease progression occurred. The main outcome was progression-free survival, defined as time from last follow-up or progression for the cohort. Adverse events were also observed. Among 16 patients with cSCC (mean [range] age, 79 [59-99] years; 9 [56%] male) who received iIL-2, the mean (range) number of treatments was 10 (2-32) and treatment duration was 13 (2-32) months. Progression-free survival was 19 months (range, 1-77 months), with a complete response rate of 81% (13 patients). Only grade 1/2 adverse events were observed. In this case series, IL-2-based immunotherapy was effective in the treatment of cSCC. With the degree of complete response observed, iIL-2 should be considered an option for patients with considerable comorbidities or with cSCC in highly sensitive areas. Additionally, given its low cost compared to systemic immunotherapy and ease of use, iIL-2 represents an option in cost-prohibitive settings. Further randomized trials are required to fully elucidate these findings.