FDG-PET parameters as predictors of pathologic response and nodal clearance in patients with stage III non-small cell lung cancer receiving neoadjuvant chemoradiation and surgery

Objective Pathologic complete response (pCR) following neoadjuvant chemoradiation (CRT) is associated with improved outcomes in stage III non-small cell lung cancer. Conflicting results exist regarding the value of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in predicting pCR. This study evaluated the association between post-CRT FDG-PET and pCR using novel FDG-PET parameters. Methods and materials This retrospective study included patients treated with CRT and resection. All underwent pre- and post-CRT FDG-PET imaging. Maximum standard uptake value (SUV_max), standard uptake ratio (SUR), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured. Results In total, 44 patients were included for review. The majority had cT2 disease (59.0%). Median radiation dose was 60 Gy (45-70.2 Gy). Rate of pCR and near-pCR within the primary lesion was 29.5% and 45.5%, respectively. Average reduction in SUV_max was 9.2, whereas SUR normalized to mediastinum and liver showed mean reductions of 4.7 and 3.5, respectively. No association was found between pCR and either MTV or TLG. Reduction in SUV_max and SUR were significantly associated with increased rate of pCR (P ≤ .02). A threshold of >75% decrease in SUR-liver showed significant association with near-pCR (diagnostic odds ratio [DOR]: 8.3; P = .007). No correlation was found between nodal FDG-PET parameters and nodal pCR. Conclusions Our results indicate SUV and SUR have utility in predicting pCR after neoadjuvant CRT. SUR parameters trended toward higher DORs, suggesting improved predictive utility compared with SUV_max. Notably, no association was found with nodal pCR. Furthermore, MTV and TLG changes were not predictive, potentially resulting from inflammation after full-dose radiation, but this warrants further investigation.