Evaluating Tumor Response of Non-Small Cell Lung Cancer Patients With 18F-Fludeoxyglucose Positron Emission Tomography: Potential for Treatment Individualization

Objective: To assess early tumor responsiveness and the corresponding effective radiosensitivity for individual patients with non-small cell lung cancer (NSCLC) based on 2 successive F-18-fludeoxyglucose positron emission tomography (FDG-PET) scans. Methods and Materials: Twenty-six NSCLC patients treated in Maastricht were included in the study. Fifteen patients underwent sequential chemoradiation therapy, and 11 patients received concomitant chemoradiation therapy. All patients were imaged with FDG before the start and during the second week of radiation therapy. The sequential images were analyzed in relation to the dose delivered until the second image. An operational quantity, effective radiosensitivity, alpha(eff), was determined at the voxel level. Correlations were sought between the average aeff or the fraction of negative aeff values and the overall survival at 2 years. Separate analyses were performed for the primary gross target volume (GTV), the lymph node GTV, and the clinical target volumes (CTVs). Results: Patients receiving sequential treatment could be divided into responders and nonresponders, using a threshold for the average alpha(eff) of 0.003 Gy(-1) in the primary GTV, with a sensitivity of 75% and a specificity of 100% (P<. 0001). Choosing the fraction of negative alpha(eff) as a criterion, the threshold 0.3 also had a sensitivity of 75% and a specificity of 100% ( P<. 0001). Good prognostic potential was maintained for patients receiving concurrent chemotherapy. For lymph node GTV, the correlation had low statistical significance. Across-validation analysis confirmed the potential of the method. Conclusions: Evaluation of the early response in NSCLC patients showed that it is feasible to determine a threshold value for effective radiosensitivity corresponding to good response. It also showed that a threshold value for the fraction of negative alpha(eff) could also be correlated with poor response. The proposed method, therefore, has potential to identify candidates for more aggressive strategies to increase the rate of local control and also avoid exposing to unnecessary aggressive therapies the majority of patients responding to standard treatment. (C) 2015 Elsevier Inc.