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

Abstract

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 [18F]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.

Positron emission tomography/computed tomography for osseous and soft tissue sarcomas: A systematic review of the literature and meta-analysis

“…Of the 1,310 articles screened, 16 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) were selected for the final analysis (Fig. 1).…”

“…Currently, radiographic tests such as X-ray, CT and MRI are widely applied for the diagnosis and treatment of musculoskeletal system malignancies (22). 18 F-fluorodeoxyglucose (FDG) PET is used for the semiquantification of glucose consumption by cells in the body, which makes it possible to measure the enhancement of metabolic activity in cancer tissue. This is normally performed by calculating the SUVmax.…”

“…This is normally performed by calculating the SUVmax. 18 F-FDG PET has been successfully used for the diagnosis of several types of cancer, such as lung cancer, melanoma, lymphoma, head and neck tumors, brain tumors, esophageal and colorectal cancer (23). The majority of the studies on the diagnostic value of PET in different types of tumors have concluded that it is a sensitive imaging modality for detection, staging and re-staging in oncology (24)(25)(26).…”

“…However, although 18 F-FDG may locate abnormally functioning anatomical structures, the precise localization of the tumors may not be possible with PET alone. Combining PET with a high-resolution anatomical imaging modality, such as CT, addresses this issue, provided that the images from the two modalities are accurately co-registered.…”

Neoadjuvant Chemotherapy for Soft Tissue Sarcoma of the Extremity or Trunk, Gastrointestinal Stromal Tumors, and Retroperitoneal Sarcoma

“…Dynamic positron emission technology (PET) imaging is being used to evaluate treatment responses after initial cycles of neoadjuvant chemotherapy (Dimitrakopoulou-Strauss et al, 2010). Further, there does appear to be a histopathologic correlation of treatment response and PET imaging which may allow early treatment decisions as to continuing or discontinuing neoadjuvant chemotherapy (Benz et al, 2009). …”