FDG-PET/CT Imaging Predicts Histopathologic Treatment Responses after the Initial Cycle of Neoadjuvant Chemotherapy in High-Grade Soft-Tissue Sarcomas.

Authors' Affiliations: Ahmanson Biological Imaging Division, Department of Molecular and Medical Pharmacology; Divisions of Medical Oncology and Orthopedic Oncology; Departments of Pathology, Biostatistics, and Radiology; and Division of Surgical Oncology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California and Abteilung Nuklearmedizin, University of Freiburg, Freiburg, Germany.

PURPOSE: In patients with soft-tissue sarcoma (STS), the early assessment of treatment responses is important. Using positron emission tomography/computed tomography (PET/CT) with [(18)F]fluorodeoxyglucose (FDG), we determined whether changes in tumor FDG uptake predict histopathologic treatment responses in high-grade STS after the initial cycle of neoadjuvant chemotherapy.

EXPERIMENTAL DESIGN: From February 2006 to March 2008, 50 patients with resectable high-grade STS scheduled for neoadjuvant therapy and subsequent tumor resection were enrolled prospectively. FDG-PET/CT before (baseline), after the first cycle (early follow-up), and after completion of neoadjuvant therapy (late follow-up) was done. Tumor FDG uptake and changes were measured by standardized uptake values. Histopathologic examination of the resected specimen provided an assessment of treatment response. Patients with >/=95% pathologic necrosis were classified as treatment responders. FDG-PET/CT results were compared with histopathologic findings.

RESULTS: At early follow-up, FDG uptake decreased significantly more in 8 (16%) responders than in the 42 (84%) nonresponders (-55% versus -23%; P = 0.002). All responders and 14 of 42 nonresponders had a >/=35% reduction in standardized uptake value between baseline and early follow-up. Using a >/=35% reduction in FDG uptake as early metabolic response threshold resulted in a sensitivity and specificity of FDG-PET for histopathologic response of 100% and 67%, respectively. Applying a higher threshold at late follow-up improved specificity but not sensitivity. CT had no value at response prediction.

CONCLUSION: A 35% reduction in tumor FDG uptake at early follow-up is a sensitive predictor of histopathologic tumor response. Early treatment decisions such as discontinuation of chemotherapy in nonresponding patients could be based on FDG-PET criteria.

PMID: 19351756 [PubMed - as supplied by publisher]