Disease Burden on PET Predicts Outcomes for Advanced NSCLC Patients Treated with First-Line Immunotherapy

Background: First-line immunotherapy (IMT), with or without cytotoxic chemotherapy, is now recommended for most patients with advanced non-small cell lung cancer (NSCLC) with no targetable mutations. We reviewed outcomes for NSCLC patients treated with first-line IMT at our institution to test the hypothesis that measures of disease burden on staging FDG-PET/CT have prognostic value. Materials and Methods: Patient, disease, and treatment details were collected. A gradient-based segmentation tool was used to delineate each PET-avid extracranial lesion. Numbers of extrathoracic lesions and metabolic tumor volumes were tabulated. Oligometastatic disease (OMD) was defined as having ≤3 extrathoracic lesions, with any number of thoracic lesions. Progression-free survival (PFS) and overall survival (OS) rates following initiation of IMT were evaluated using the Kaplan-Meier method, and predictors of PFS and OS were assessed using Cox proportional hazards models and logrank tests. Results: One hundred twenty-four patients met inclusion criteria, and 1143 lesions were contoured. The presence of OMD was associated with favorable PFS (median 13.1 vs. 6.9 months; P = .016) and favorable OS (median 36.5 vs. 15.4 months; P = .002). In multivariable models, OMD was associated with favorable PFS (HR = 0.64; P = .034) and favorable OS (HR = 0.61; P = .063), and metabolic tumor volumes exceeding the cohort median (88 cc) was associated with inferior OS (HR = 1.85; P = .028). Conclusion: For advanced NSCLC patients receiving first-line IMT, the presence of extrathoracic OMD and low volumetric disease burden on PET are favorable prognostic factors that could be useful stratification factors in clinical trials and may influence clinical decisions about local and systemic therapy.