Prospective evaluation of metabolic intratumoral heterogeneity using 18F-FDG-PET-CT in patients with advanced gastric cancer receiving palliative chemotherapy.

Abstract

4059 Background: Metabolic intratumoral heterogeneity (ITH) gives important information on treatment response and prognosis. However, temporal changes in metabolic ITH and their associations with treatment outcome have not been reported yet in gastric cancer (GC). We aimed to evaluate the early changes in metabolic ITH and their predictive roles in advanced GC patients receiving palliative chemotherapy. Methods: Unresectable locally advanced or metastatic GC patients were prospectively enrolled before the first-line palliative chemotherapy and underwent 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET-CT) at baseline (T1) and at the first response evaluation follow-up (T2). SUVs (Standardized uptake values), volumetric parameters, and textural features including entropyHisto and contrastGLCM were extracted from the primary gastric tumor at T1, T2, and ΔT (T2-T1) was evaluated. Associations of these parameters with treatment response, progression-free survival (PFS), and overall survival (OS) were analyzed. Results: 87 patients were analyzed. Of 86 evaluable patients, 44 obtained partial response, 33 stable disease, and 8 progressed. The objective response rate was 51.8% (95% confidence interval [CI], 40.7% to 62.7%). The median PFS and OS were 7.3 months (95% CI, 5.4 to 8.2 months) and 11.5 months (95% CI, 10.1 to 14.3 months), respectively. From T1 to T2, metabolic ITH was significantly reduced ( P < 0.01), and the degree of decrease was greater in responders than in non-responders ( P < 0.01). By multiple Cox regression analyses adjusted for clinical variables, low entropyHisto at T2 ( P= 0.001), larger decreases in coefficient of variance ( P= 0.003) and contrastGLCM ( P= 0.017) were associated with better PFS. Low SUVpeak at T2 ( P= 0.001), larger decreases in coefficient of variance ( P= 0.032) and being a responder were associated with better OS. Conclusions: Early reduction in metabolic ITH is useful to predict response to palliative chemotherapy, PFS and OS in advanced GC patients.