Necrosis on pre-radiotherapy 18F-FDG PET/CT is a predictor for complete metabolic response in patients with non-small cell lung cancer

To investigate necrosis on pre-radiotherapy (RT) F-18-FDG PET/CT (PETNECROSIS) as a predictor of complete metabolic response (CMR) in patients with non-small cell lung cancer (NSCLC). We evaluated patients with inoperable stage I-III NSCLC who underwent pre- and post-radiotherapy F-18-FDG PET/CT. The relationship between CMR and PETNECROSIS, SUVmax, gross tumor volume calculated with F-18-FDG PET/CT (GTV(PET-CT)), tumor size, histology, metabolic tumor volume (MTV), and RT dose was assessed using logistic regression analysis. To evaluate necrosis on F-18 FDG PET/CT, we drew a region of interest (ROI) in the area showing visually very low/or no fluorodeoxyglucose (FDG) uptake on PET images. If the SUVmax was lower than the blood pool SUVmax and showed significantly lower attenuation (10-30 Hounsfield units [HU]) from the surrounding tissue on non-intravenous contrast-enhanced low-dose correlative CT, we defined it as necrotic (PETNECROSIS). Fifty-three patients were included in this study. The mean age was 68.1 +/- 9.8 years. Twenty-one patients had adenocarcinoma, and 32 had squamous cell carcinoma. All parameters were independent of histologic status. Multivariate logistic regression analysis showed that SUVmax <= 11.6 vs >11.6, (P = .003; OR, 7.670, 95CI%: 2.013-29.231) and PETNECROSIS absence/presence were independent predictors for CMR (P = .028, OR: 6.704, 95CI% 1.214-30.394). The necrosis on F-18 FDG PET/CT and SUVmax > 11.6 could be an imaging marker for the complete metabolic response after definitive chemoradiotherapy or definitive RT alone in patients with NSCLC.