A rationale for surgical debulking to improve anti-PD1 therapy outcome in non small cell lung cancer.

Anti-PD1 immunotherapy has emerged as a gold-standard treatment for first- or second-line treatment of stage IV NSCLC, with response rates ranging from 10 to 60%. Strategies to improve the disease control rate are needed. Several reports suggested that debulking surgery enhances anti-tumor immunity. We aimed at examining tumor burden as a predictive factor of anti-PD1 tretment efficacy and to evaluate the role of cytoreductive surgery in anti-PD1 treated NSCLC. Immunocompetent DBA/2 mice engrafted with various amount of allogeneic lung squamous cancer KLN-205 cells were treated with anti-PD1 monoclonal antibody. Mice engrafted with two tumors also underwent a debulking surgery or a sham procedure. Tumor volume was monitored to assess treatment efficacy. Tumor infiltrating lymphocytes were assessed by flow cytometry. In a retrospective study of 48 stage IV NSCLC patients treated with Nivolumab who underwent a 18-FDG PETscan before treatment onset, the prognostic role of metabolic tumor volume was analysed. Anti-PD1 treatment effect was greater in mice bearing smaller tumors. Treatment with higher doses of anti-PD1 antibody did not improve the outcome, independently of the size of the tumor. In mice bearing 2 tumors, excision of 1 tumor improved the anti-PD1 treatment effect on the remaining tumor. In 48 NSCLC patients receiving anti-PD1 treatment, high metabolic tumor volume was associated with poor overall survival and the absence of clinical benefit. Treg infiltration, but not effector T cells, was positively correlated to tumor volume. Taken together, our results suggest that tumor volume is a predictive factor of anti-PD1 efficacy in NSCLC. Additionally, an experimental murine model suggests that tumor debulking may improve control of residual tumor.