Association of reduction of tumor metabolism with prognosis of advanced gastric cancer patients treated with palliative chemotherapy: Prospective cohort study.

Abstract

31 Background: Although tumor metabolism can be measured by 18F-FDG PET, the meaning of metabolic response by chemotherapy in gastric cancer patients has not been well studied. The purpose of this study is to identify prognostic value of tumor metabolic response in gastric cancer. Methods: Advanced gastric cancer patients were enrolled in this prospective cohort study before initiation of palliative chemotherapy. At the baseline and at the first tumor response evaluation, 18F-FDG PET was taken to measure tumor metabolism. We measured maximum standardized uptake value (SUVmax), and total lesion glycolysis (TLG) calculated as multiplying mean SUV by metabolic tumor volume (MTV) using threshold SUVs of 2.5 (TLG2.5) in each patients. Correlation of clinicopathological factors and survival were analyzed. Results: A total of 87 patients were enrolled. Baseline high SUVmax and TLG2.5 were associated with HER2 positivity, histologic differentiation and tumor size. High SUVmax and TLG2.5 were also associated with worse overall survival (OS) (HR 2.14, P = 0.025; HR 2.23, P = 0.037, respectively). Comparing RECIST evaluation, 30% of the reduction of sum of target lesions was correlated with 50% reduction of SUVmax, and 50% reduction of TLG2.5. The larger reduction of SUVmax (HR 0.43, P = 0.006 for Progression-free survival (PFS); HR 0.38, P = 0.007 for OS), and TLG2.5 (HR 0.27, P < 0.001 for PFS; HR 0.27, P = 0.001 for OS) was associated with better OS. In multivariate analysis, SUVmax and TLG2.5 were independent prognostic factors along with age, histologic type, gastrectomy history and HER2 status. Conclusions: Tumor metabolic response measured by SUVmax or TLG2.5 was associated with prognosis of advanced gastric cancer patients treated with chemotherapy.