Prediction of survival by [¹⁸F]fluorodeoxyglucose positron emission tomography in patients with locally advanced non-small-cell lung cancer undergoing definitive chemoradiation therapy: Results of the ACRIN 6668/RTOG 0235 trial

Purpose: In this prospective National Cancer Institute-funded American College of Radiology Imaging Network/Radiation Therapy Oncology Group cooperative group trial, we hypothesized that standardized uptake value (SUV) on post-treatment [¹⁸F]fluorodeoxyglucose positron emission tomography (FDG-PET) correlates with survival in stage III non-small-cell lung cancer (NSCLC). Patients and Methods: Patients received conventional concurrent platinum-based chemoradiotherapy without surgery; postradiotherapy consolidation chemotherapy was allowed. Post-treatment FDG-PET was performed at approximately 14 weeks after radiotherapy. SUVs were analyzed both as peak SUV (SUV_peak) and maximum SUV (SUV_max; both institutional and central review readings), with institutional SUV_peak as the primary end point. Relationships between the continuous and categorical (cutoff) SUVs and survival were analyzed using Cox proportional hazards multivariate models. Results: Of 250 enrolled patients (226 were evaluable for pretreatment SUV), 173 patients were evaluable for post-treatment SUV analyses. The 2-year survival rate for the entire population was 42.5%. Pretreatment SUV_peak and SUV_max (mean, 10.3 and 13.1, respectively) were not associated with survival. Mean post-treatment SUV_peak and SUV_max were 3.2 and 4.0, respectively. Post-treatment SUV_peak was associated with survival in a continuous variable model (hazard ratio, 1.087; 95% CI, 1.014 to 1.166; P = .020). When analyzed as a prespecified binary value (≤ v > 3.5), there was no association with survival. However, in exploratory analyses, significant results for survival were found using an SUV_peak cutoff of 5.0 (P = .041) or 7.0 (P < .001). All results were similar when SUV_max was used in univariate and multivariate models in place of SUV_peak. Conclusion: Higher post-treatment tumor SUV (SUV_peak or SUV_max) is associated with worse survival in stage III NSCLC, although a clear cutoff value for routine clinical use as a prognostic factor is uncertain at this time.