Abstract
BackgroundThis study aimed to evaluate the prognostic value of pretreatment 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with localized primary gastrointestinal stromal tumors (GISTs) and to compare the predictive values of 18F-FDG PET/CT parameters with those of clinicopathological prognostic factors.MethodsSixty-two localized GIST patients who underwent staging with 18F-FDG PET/CT from January 2007 to December 2013 before surgery were retrospectively enrolled. A volume of interest with a standardized uptake value (SUV) threshold of 2.5 was used to determine the metabolic tumor volume (MTV) and total lesion glycolysis (TLG). These metabolic indices, along with the maximum SUV (SUVmax), were analyzed to evaluate recurrence-free survival (RFS). Other significant clinical and pathologic indices were also retrospectively reviewed for RFS analysis.ResultsPatients were followed up for a median of 42.0 months (range, 5.6–111.5). During the follow-up period, 13 patients (21.0%) experienced disease recurrence. In univariate analysis, tumor size (> 5 cm), mitotic count (> 5/high-power field), modified National Institutes of Health (NIH) consensus criteria, adjuvant imatinib treatment, SUVmax (≥ 7.04), MTV (≥ 50.76 cm3), and TLG (≥ 228.79 g) were significant prognostic factors affecting RFS (p < 0.05). In multivariate analysis, only MTV (hazard ratio, 17.69; 95% confidence interval [CI], 2.03–154.17, p = 0.009) and TLG (hazard ratio, 20.48; 95% CI, 2.19–191.16, p = 0.008) were independent prognostic factors for RFS. The 5-year RFS rates were 96.4% and 96.6% in patients with a low MTV and TLG and 27.3% and 23.6% in patients with a high MTV and TLG, respectively (p < 0.001).ConclusionMTV and TLG are independent prognostic factors for predicting recurrence in patients with localized primary GIST. Patients with a high MTV or TLG are at risk for poor prognosis and should be closely observed for disease recurrence.
Highlights
This study aimed to evaluate the prognostic value of pretreatment 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG 18F-Fluorodeoxyglucose positron emission tomography/ computed tomography (PET/Computed tomography (CT))) in patients with localized primary gastrointestinal stromal tumors (GISTs) and to compare the predictive values of 18F-FDG Positron emission tomography (PET)/CT parameters with those of clinicopathological prognostic factors
Due to KIT proto-oncogene or platelet-derived growth factor receptor α (PDGFRα) mutations in GIST [5, 6], targeted therapy using imatinib mesylate (Gleevec®, Novartis Pharmaceuticals, Basel, Switzerland), a selective inhibitor of KIT and PDGFRα proteins, has been shown to prolong recurrence-free survival (RFS) in those at high risk for recurrence when used in an adjuvant therapy setting [7]
Current guidelines for risk stratification of GIST are based on tumor size and mitotic count, primary tumor location, and tumor rupture [8,9,10], most of which are assessed based on pathologic specimens
Summary
This study aimed to evaluate the prognostic value of pretreatment 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with localized primary gastrointestinal stromal tumors (GISTs) and to compare the predictive values of 18F-FDG PET/CT parameters with those of clinicopathological prognostic factors. Current guidelines for risk stratification of GIST are based on tumor size and mitotic count, primary tumor location, and tumor rupture [8,9,10], most of which are assessed based on pathologic specimens. 18F-FDG PET/CT findings may be better at predicting RFS than the current guidelines, as global tumor glycolysis is readily assessed using volumetric parameters, such as metabolic tumor volume (MTV) or total lesion glycolysis (TLG), in contrast to mitotic count, which has been shown to be inhomogeneous in larger GISTs [17, 18]. 18F-FDG PET/CT may be helpful in guiding pathologists in the identification of areas with high glycolysis, as these areas may have a higher Ki-67 expression
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