Atypical Response in Metastatic Non-Small Cell Lung Cancer Treated with PD-1/PD-L1 Inhibitors: Radiographic Patterns and Clinical Value of Local Therapy

Purpose: To explore the clinical characteristics, management, and survival outcomes of advanced NSCLC patients treated with PD-1/PD-L1 inhibitors who presented with an atypical response (AR). Methods: A total of 926 PD-1/PD-L1-inhibitor-treated patients with metastatic NSCLC from three academic centers were retrospectively reviewed. All measurable lesions were evaluated by RECIST version 1.1. Results: Fifty-six (6.1%) patients developed AR. The median time to the occurrence of AR was 2.0 months. Patients with no fewer than 3 metastatic organs at baseline were more prone to develop AR in advanced NSCLC (p = 0.038). The common sites of progressive lesions were lymph nodes (33.8%) and lungs (29.7%). The majority (78.2%) of patients with AR had only 1–2 progressive tumor lesions, and most (89.1%) of the progressive lesions developed from originally existing tumor sites. There was no significance in terms of survival between patients with AR and those with typical response (TR). Local therapy was an independent predictor for PFS of patients with AR (p = 0.025). Conclusions: AR was not an uncommon event in patients with metastatic NSCLC treated with PD-1/PD-L1 inhibitors, and it had a comparable prognosis to those with TR. Proper local therapy targeting progressive lesions without discontinuing original PD-1/PD-L1 inhibitors may improve patient survival.