Background: Large cell neuroendocrine carcinoma (LCNEC) presents significant treatment challenges due to its rarity and limited therapeutic options. The LANCE study was designed to explore the survival benefits of incorporating atezolizumab in chemotherapy for metastatic LCNEC. Methods: In this non-randomized study, patients with metastatic LCNEC were prospectively enrolled and assigned to receive either standard chemotherapy plus atezolizumab followed by maintenance with atezolizumab or standard chemotherapy alone. The primary outcomes measured were 12- and 24-month survival rates, progression-free survival (PFS), and overall survival (OS) between the two groups. Results: Of the 22 patients screened, 17 met the inclusion criteria and received either atezolizumab plus platinum-based chemotherapy (n = 10) or chemotherapy alone (n = 7). After a median follow-up of 23.3 months, the 12-month survival rate was 57.1% (95% CI: 32.6–100%) and 14.3% (95% CI: 2.33–87.7%) for the atezolizumab and the chemotherapy-only groups, respectively. The survival benefit for the atezolizumab group was sustained at 24 months (45.7% vs. 14.3%). Overall survival was significantly higher for the atezolizumab group, and PFS was non-significantly associated with the addition of atezolizumab (log-rank p = 0.04 and 0.05, respectively). Conclusions: This pilot study suggests that the addition of atezolizumab to standard platinum-based chemotherapy may provide a substantial survival benefit compared with chemotherapy alone in the first-line treatment of metastatic LCNEC.
