The relationship between HER2 status acquired from pathological data and metabolic parameters from pre-treatment [F]FDG PET/CT in gastric adenocarcinomas.

Objective: Overexpression of Human Epidermal Growth Factor Receptor 2 (HER2) is thought to be more aggressive in gastric cancer. This study aimed to evaluate the predictability of HER2 status and other prognostic pathologic parameters using [F]FDG PET/CT and to investigate its impact on survival.

Methods: Pretreatment metabolic parameters measured by [F]FDG PET/CT as a prognostic factor were retrospectively evaluated in 117 HER2-analysed patients. The relationship between pathological data, tumor metabolic characteristics, and distant metastases was examined, and the effect on survival was investigated.

Results: Among the 117 patients, 17.1% were HER2-positive (HER2+), and 82.9% were HER2-negative (HER2-). There was no significant association between PET/CT parameters in the HER2+ and HER2- patient groups. HER2+ patients had higher 1- and 3-year survival expectations than HER2- patients (80%-%37.9; %47.5-%20; respectively). There was no statistically significant difference in overall survival. In Cox-regression analysis, while the presence of vascular invasion, local invasion, and distant metastasis were poor prognostic factors, HER2 was not a prognostic factor. Vascular invasion and local invasion (T3/T4) were also associated with higher SUVmax values. Patients with distant metastases had significantly higher SUVmax, SUVmean, and TLG.

Conclusion: This study showed no association between HER2 expression and [F]FDG PET/CT metabolic parameters. However, regardless of HER2 status, the results indicated distant metastasis, local invasion, and vascular invasion could be associated with primary tumor metabolism. PET/CT parameters predict tumor aggressiveness and disease prognosis better than HER2 status.