We present a single-arm, phase II, neoadjuvant trial with the oncolytic virus talimogene laherparepvec (T-VEC) in 18 patients with difficult-to-resect cutaneous basal cell carcinomas. The primary end point, defined as the proportion of patients, who after six cycles of T-VEC (13 weeks), become resectable without the need for plastic reconstructive surgery, was already achieved after stage I (9 of 18 patients; 50.0%); thus the study was discontinued for early success. The objective response rate was 55.6% and the complete pathological response rate was 33.3%. Secondary end points included safety, relapse-free survival and overall survival, time to occurrence of new basal cell carcinomas and biological read outs. Only mild adverse events occurred. The 6-month relapse-free survival and overall survival rates were 100%. In two patients a new basal cell carcinoma was diagnosed. T-VEC led to a significant increase in cytotoxic T cells (P = 0.0092), B cells (P = 0.0004) and myeloid cells (P = 0.0042) and a decrease in regulatory T cells (P = 0.0290) within the tumor microenvironment. Together, neoadjuvant T-VEC represents a viable treatment option for patients with difficult-to-resect basal cell carcinomas (EudraCT no. 2018-002165-19).
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