Metabolic Signature on 18F-FDG PET/CT, HER2 Status, and Survival in Gastric Adenocarcinomas

The human epidermal growth factor 2 (HER2)-overexpressing (HER2-positive [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 with HER2-negative (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 sex, there was no difference in SUV_max between HER2+ and HER2- cases (9.7 and 8.4, respectively; P = 0.6). No difference was seen between HER2+ and HER2- cases in tumor histology (81% and 57% intestinal type, respectively; P = 0.11), size (2.6 and 3.8 cm, respectively; P = 0.12), differentiation (47% and 68% poorly differentiated, respectively; P = 0.06), or presence of lymph node metastasis (60% and 40%, respectively; P = 0.3). Although 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 mo) and below (30 mo) the median SUV_max (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 a high SUV_max demonstrate a worse overall survival, suggesting that metabolic signature is a better predictor of biologic tumor aggressiveness than its histologic signature.