A recent phase II study explored the safety and efficacy of adding durvalumab (anti-PD1) and tremelimumab (anti-CTLA-4) to definitive CRT in 40 patients with locally advanced unresectable ESCC; after completing CRT with immunotherapy, the patients received two cycles of treatment with durvalumab and tremelimumab, followed by durvalumab monotherapy for up to two years after enrolment [135]. This evidence concerns the gene CTLA4 and esophageal squamous cell carcinoma.