The (18)F-FDG PET/CT response to radiotherapy for patients with spinal metastasis correlated with the clinical outcomes

PURPOSE: To evaluate the potential role of (18)F-fluorodeoxyglucose-positron emission tomography/computerized tomography (FDG-PET/CT) for predicting treatment response after radiotherapy (RT) in patients with spinal metastases. MATERIALS AND METHODS: A retrospective analysis was performed of 42 patients with spinal metastases who received RT from January 2010 to December 2014. All patients underwent FDG-PET/CT before and after treatment. Changes in metabolic responses, expressed as the maximum, mean, peak standardized uptake values (SUVmax, SUVmean, SUVpeak), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were analyzed to determine their association with clinical outcomes. RESULTS: The median age at the time of spinal metastasis diagnosis was 58 years. Median progression-free survival (PFS) and overall survival after RT were 15 months and 22.4 months, respectively. RT produced a significant decrease in SUVmean (2.27 to 1.41), SUVmax (6.87 to 2.99), SUVpeak (5.75 to 2.33) and TLG (52.84 to 24.17) when compared with the baseline values (p<0.001). The mean pain score decreased from 3.86 before RT to 0.79 after RT (p<0.001). There were significant linear relationships between maximum SUV and pain scores at baseline (r = 0.321, p = 0.038) and after treatment (r = 0.369, p = 0.016) as well as TLG at baseline (r = 0.428, p = 0.005) and after treatment (r = 0.403, p = 0.009). Local progression after treatment was identified in 12 patients (28.6%). Univariate analyses showed that >70% reduction in maximum SUV after treatment was independently associated with good PFS (p = 0.036). CONCLUSIONS: RT is an effective treatment for patients with spinal metastases, and there were significant changes in PET parameters compared with baseline. The metabolic response measured by SUV and TLG changes in FDG-PET/CT correlated with the clinical outcomes, especially with shorter PFS in patients who had higher residual maximum SUV after treatment.