Tumor Response Dynamics of Advanced Non-small Cell Lung Cancer Patients Treated with PD-1 Inhibitors: Imaging Markers for Treatment Outcome

Purpose: We evaluated tumor burden dynamics in patients with advanced non-small cell lung cancer (NSCLC) treated with commercial PD-1 inhibitors to identify imaging markers associated with improved overall survival (OS). Experimental Design: The study included 160 patients with advanced NSCLC treated with commercial nivolumab or pembrolizumab monotherapy as a part of clinical care. Tumor burden dynamics were studied for the association with OS. Results: Tumor burden change at best overall response (BOR) ranged from -100% to +278% (median, +3.5%). Response rate (RR) was 18% (29/160). Current and former smokers had a higher RR than never smokers (P = 0.04). Durable disease control for at least 6 months was noted in 26 patients (16%), which included 10 patients with stable disease as BOR. Using a landmark analysis, patients with < 20% tumor burden increase from baseline within 8 weeks of therapy had longer OS than patients with >= 20% increase (median OS, 12.4 vs. 4.6 months, P < 0.001). Patients with < 20% tumor burden increase throughout therapy had significantly reduced hazards of death (HR, 0.24; Cox P < 0.0001) after adjusting for smoking (HR, 0.86; P = 0.61) and baseline tumor burden (HR, 1.55; P = 0.062), even though some patients met criteria for RECIST progression while on therapy. One patient (0.6%) had atypical response pattern consistent with pseudoprogression. Conclusions: Objective response or durable disease control was noted in 24% of patients with advanced NSCLC treated with commercial PD-1 inhibitors. A tumor burden increase of < 20% from baseline during therapy was associated with longer OS, proposing a practical marker of treatment benefit. Pseudoprogression is rare in NSCLCs treated with PD-1 inhibitors. (C) 2017 AACR.