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<0.01, five-year RFS: 80.0% vs. 21.7% P < 0.01). A multivariate analysis for the RFS revealed that adjuvant chemotherapy was a significant independent prognostic factor among patients with DLL3-negative tumors (hazard ratio [HR]: 0.05, 95% confidence interval [CI]: 0.01–0.41, P < 0.01), although it was not a factor among patients with DLL3-positive tumors (HR: 0.73, 95% CI: 0.23–2.27, P = 0.58). Conclusions: Our results revealed that DLL3 is a predictive marker of sensitivity to platinum-based adjuvant chemotherapy for LCNEC. Key points: Significant findings of the study: DLL3 was a predictive marker of sensitivity to platinum-based adjuvant chemotherapy for LCNEC. Among patients with DLL3 expression-negative LCNEC, platinum-based adjuvant chemotherapy significantly improved the OS and RFS, although it did not do so among patients with DLL3 expression-positive LCNEC. What this study adds: Our results suggest that DLL3 expression-positive LCNEC may be better treated with other types of adjuvant chemotherapy, such as the anti-DLL3 therapies if these effects are confirmed by ongoing clinical research.