DLL3 expression is a predictive marker of sensitivity to adjuvant chemotherapy for pulmonary LCNEC

Background The mammalian Notch family ligands delta‐like 3 (DLL3) is reported to be a potential therapeutic target for large cell neuroendocrine carcinomas (LCNEC). The effect of DLL3 expression on LCNEC prognosis has not yet been elucidated. Methods We reviewed the medical records of 70 LCNEC patients undergoing surgical resection between 2001 and 2015 using a prospectively maintained database. We performed immunohistochemistry for DLL3 and investigated the correlation between the sensitivity of LCNEC to platinum‐based adjuvant chemotherapy. Results DLL3 expression was positive in 26 (37.1%) LCNEC patients. A total of 23 patients (32.9%) received platinum‐based adjuvant chemotherapy. Among patients with DLL3 expression‐positive tumors, no difference was found in the five‐year overall survival (OS) or recurrence‐free survival (RFS) between patients with and without adjuvant chemotherapy (surgery + chemotherapy vs. surgery alone, five‐year OS: 58.3% vs. 35.7% P = 0.36, five‐year RFS: 41.7% vs. 35.7% P = 0.74). In contrast, among patients with DLL3‐negative tumors, significantly greater five‐year OS and RFS rates were observed for patients with adjuvant chemotherapy than for those without it (surgery + chemotherapy vs. surgery alone: five‐year OS: 90.0% vs. 26.9% P