Stage Migration in Planning PET/CT Scans in Patients Due to Receive Radiotherapy for Non-Small-Cell Lung Cancer

Currently, controversy surrounds how long a delay is needed to affect the results of radiochemotherapy in patients with non-small-cell lung cancer. The present findings suggest that delays of just 6 weeks may degrade treatment efficacy. In 26% of the patients, TNM stage progression changed treatment intent after a repeat PET/CT scan taken, on median, 45 days after the initial scan. Introduction: This study examined rates of tumor progression in treatment-naive patients with non-small-cell lung cancer (NSCLC) as determined by repeat treatment-planning fluorine-18 (F-18) fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT). Methods and Materials: This study assessed patients who underwent PET/CT simulation for NSCLC stage II/III, radiation-naive, nonmetastatic NSCLC. It compared planning PET/CT with previous PET/CT images. Patients were analyzed for change in stage, treatment intent, or both. Progression was defined as a change in TNM status leading to upstaging, and standardized uptake value (SUV) velocity was defined as [(SUVscan2 - SUVscan1)/interscan interval in days]. Results: Of 149 consecutive patients examined between April 2009 and April 2011, 47 had prior PET/CT scans and were included. The median age was 68 years. New nodal disease or metastatic disease was identified in 24 (51%) of 47 patients. Fourteen (30%) had evidence of extrathoracic metastatic disease; the remaining 10 (21%) had new nodal disease that required substantial alteration of treatment fields. At a scan interval of 20 days, the rate of upstaging was 17%. SUV velocity was analyzed in the subset of patients who had their studies on the identical PET/CT scanner (n = 14). Nonupstaged patients had a mean SUV velocity of 0.074 units per day, compared with 0.11 units per day in patients that were upstaged by their second PET/CT scan (P = .020). Conclusion: Radiation treatment planning with hybrid PET/CT scans repeated within 120 days of an initial staging PET/CT scan identified significant upstaging in more than half of patients. For a subset of patients who underwent both scans on the same instrument, SUV velocity predicts upstaging, and the difference between those upstaged and those not was statistically significant. (C) 2014 Elsevier Inc. All rights reserved.