Prognostic value of pretreatment metabolic tumor volume on [S-methyl-11C]-L-methionine PET/CT in patients with local non-small cell lung carcinoma treated with single-fraction carbon-ion radiotherapy

Purpose: This study aimed to evaluate the prognostic predictive ability of MET-PET/CT-derived imaging biomarkers in patients with localized non-small cell lung cancer (NSCLC) undergoing single-fraction carbon-ion radiotherapy (CIRT) and to clarify the additional prognostic information these biomarkers can provide beyond the standard UICC staging protocol. Methods: With institutional review board approval, 67 localized NSCLC patients eligible for CIRT between 2007 and 2012 were included. Single-fraction doses of 40-50 Gy were irradiated. MET-PET imaging using the Toshiba Aquiduo or Siemens Biograph 16 commenced 20 minutes post 740MBq MET injection before CIRT. Experienced radiologists analyzed the images, defining metabolic tumor volume (MTV) as areas with SUV >1.5. Statistical analysis was performed using SPSS 29, including Cox proportional hazard models for disease-free and overall survival. Results: Seven cases with Tis of T stage were excluded because of low MET radiotracer uptake. A total of 60 patients were analyzed: 36 males and 24 females with a mean age of 73 years; 35 cases of T1, 24 cases of T2, and one T3 case. The average follow-up period was 74.3 months. The univariate Cox proportional hazard analyses showed that SUVmax, MTV, and total lesion retention (TLR) correlated with disease-free survival (DFS), while no significant difference was noted in treatment dose. For overall survival (OS), solid tumor diameter, SUVmax, MTV, TLR, and sex showed significant correlations in the univariate analysis. The multivariate analysis identified MTV as the only significant prognostic factor for both DFS and OS. Kaplan-Meier survival curves further supported these findings, with log-rank tests indicating a significant difference in survival duration related to MTV in both DFS and OS. Conclusion: MTV in pretreatment MET-PET/CT would be a valuable predictor of DFS and OS of localized NSCLC treated with single-fraction CIRT.