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

SIMPLE SUMMARY: The emergence of atypical response (AR) has challenged the process of response evaluation and the subsequent management of non-small cell lung cancer (NSCLC) patients treated with PD-1/PD-L1 inhibitors. We conducted a multicenter retrospective analysis and found that AR was not an uncommon event in patients with metastatic NSCLC treated with the PD1/PD-L1 inhibitor. The median time to AR occurrence was 2.0 months, and patients with ≥3 metastatic organs at baseline were more likely to develop AR. For patients with AR, the common sites of progressive lesions were the lymph nodes and lungs. Furthermore, the majority of patients with AR had only 1–2 progressive tumor lesions, and most of the progressive lesions developed from originally existing tumor sites. Patients with AR had a comparable prognosis to those with a typical response (TR). Proper local therapy targeting progressive tumor lesions while maintaining the PD1/PD-L1 inhibitor may be a feasible treatment selection for patients with AR. ABSTRACT: 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.