18 F-FDG PET-CT: Predicting recurrence in patients following percutaneous cryoablation treatment for stage i primary non-small-cell lung cancer

Purpose The aim of this study was to understand the imaging features of fluorine-18 fluorodeoxyglucose (18 F-FDG) PET-computed tomography (CT) in postcryoablation lung cancer patients that could help predict recurrence. Methods We identified 28 patients with 30 lesions treated by means of percutaneous cryoablation for stage I non-small-cell lung cancer. Two experienced nuclear radiologists blindly reviewed baseline images and follow-up 18 F-FDG PET-CT scans for a minimum of 24 months, with discrepancy in interpretation resolved by consensus. Nineteen lesions had undergone baseline PET-CT studies, whereas 11 lesions had undergone only baseline CT studies. Follow-up PET-CT studies were analyzed for up to 24 months, whereas the recurrence-free survival analysis was performed for 36 months. Results The average maximum standardized uptake value (SUV max) at baseline (n=19) was 5.2±3.9 and the average CT area at baseline was 2.2±1.6 cm 2. Only the CT area was significantly different between recurring and nonrecurring lesions at baseline (P=0.0028). The Kaplan-Meier survival analysis showed that dichotomizing lesions around 2 cm on CT did not result in a statistically significant survival difference (hazard ratio=1.42, 95% confidence interval: 0.63-2.21). The average SUV max at first follow-up was 1.9±1.8 for 27 lesions, whereas the average SUV max of recurrent lesions was 2.2±2.2 and that of nonrecurrent lesions was 1.5±0.3 (P=0.17). Six lesions had SUV max more than or equal to 2.5 within 24 months, all of which recurred in the ablation zone. Conclusion 18 F-FDG PET-CT is a valuable tool for determining treatment response and for distinguishing benign from malignant lesions after cryoablation. The CT area was most predictive of future recurrence at baseline, whereas SUV max more than or equal to 2.5 was most predictive of future recurrence at first follow-up.