Metabolic Signature on FDG PET/CT, HER2 Status and Survival in Gastric Adenocarcinoma

Abstract

The human epidermal growth factor 2 (HER2) overexpressing (HER2+) gastric (GC) and gastroesophageal junction adenocarcinomas (GEJC) are felt to represent a more aggressive form of disease, which may correlate to increased metabolic activity. Whether tumor SUV_max measured by ¹⁸F-FDG PET/CT, could be a preoperative parameter used to predict HER2 status of GC/GEJC is unknown. Methods: Pathology reports of HER2+ GC/GEJC biopsies and resections from 31 patients, were reviewed and compared to HER2- cases distributed evenly over the same time period. We analyzed their SUV_max intensity and then compared the HER2 status and SUV_max parameters and their association with survival. Results: After matching for age and gender, there was no difference in SUV_max between HER2+ and HER2- cases (9.7 and 8.4, P = 0.6). No difference was seen between HER2+ and HER2- cases in tumor histology (81% and 57% intestinal type, P = 0.2), size (2.6 and 3.8 cm, P = 0.12), differentiation (47% and 68% poorly differentiated, P = 0.06), or presence of lymph node metastasis (60% and 40%, P = 0.3). While there was no difference in survival demonstrated by HER2+ and HER2- cases, there was a significant difference in survival between SUV_max above (12.2 months) and below (30 months) the median SUV_max value (6.6, P = 0.01). Conclusion: Our study shows that SUV_max is not associated with HER2 status of GC/GEJC. Independent of HER2 overexpression, patients with high SUV_max demonstrate a worse overall survival, suggesting that metabolic signature is a better predictor of biologic tumor aggressiveness than its histological signature.