¹⁸F-FDG-PET/CT imaging as an early survival predictor in patients with primary high-grade soft tissue sarcomas undergoing neoadjuvant therapy

Purpose: Neoadjuvant therapy is associated with considerable toxicity and limited survival benefits in patients with soft tissue sarcoma (STS). We prospectively evaluated whether 2[18F]fluoro-2-deoxy-D-glucose ( ¹⁸F-FDG)-PET/computed tomographic (CT) imaging after the initial cycle of neoadjuvant therapy could predict overall survival in these patients. Experimental Design: Thirty-nine patients underwent ¹⁸F-FDG-PET/CT before and after one cycle of neoadjuvant therapy. Fifty-six patients underwent end-of-treatment PET. Overall survival was, among others, correlated with changes of SUV _peak and histopathology. Results: One-, two-, and five-year survival rates were 95% ± 3.0%, 86% ± 4.6%, and 68% ± 6.6%, respectively. Median time to death was 30.9 months (mean, 27.7; range, 6.9-50.1). Optimal cutoff values for early and late decreases in SUV _peak (26% and 57%, respectively) were significant predictors of survival in univariate survival analysis [P = 0.041; HR, 0.27; 95% confidence interval (CI), 0.08-0.95 and P = 0.045; HR, 0.31;95%CI, 0.10-0.98]. Seven of 15 early PET nonresponders but only four of 24 early PET responders died during follow-up (P = 0.068). The only other significant survival predictor was surgical margin positivity (P = 0.041; HR, 3.31; 95% CI, 1.05-10.42). By multivariable analysis, early metabolic response (P = 0.016) and positivity of surgical margins (P = 0.036) remained significant survival predictors. Conclusion: ¹⁸F-FDG-PET predicted survival after the initial cycle of neoadjuvant chemotherapy in patients with STS and can potentially serve as an intermediate endpoint biomarker in clinical research and patient care.