The Relationship Between HER-2 Expression Levels and ¹⁸F-FDG PET/CT Parameters in Gastric Cancer

Human epidermal growth factor receptor-2 (HER-2) is a protooncogene encoded by ERBB2 on chromosome 17. ¹⁸Fluoridefluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) examination is frequently used to detect distant metastasis in gastric cancer imaging. This study aimed to investigate the relationship between the data obtained in the ¹⁸F-FDG PET/CT examination and HER-2 expression status in patients with gastric cancer.

A total of 115 patients diagnosed with gastric cancer between 2016 and 2020, with HER-2 immunohistochemical followed by ¹⁸F-FDG PET/CT examination for staging purposes were included.

HER-2 immunohistochemical examination revealed 71 patients (61.7%) with negative and 44 (38.3%) with positive results. The median maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) values of patients positive with HER-2 were 9.95, 5, 30.44, and 139.16, respectively, whereas patients negative with HER-2 were 9.3,5.4,36.62, and 190.424, respectively (p>0.05). The median cancer antigen 19-9 (CA 19-9) levels of patients positive with HER-2 was 33.52, whereas 11.79 in those who were negative (p=0.016). The mean age was 69.3±9.35 years in patients with distant metastases, whereas 65.2±10.9 in those without distant metastases (p=0.042). Median SUV_max and SUV_mean values in patients with distant metastases were 11.1 and 6.3, respectively, and 8.2 and 4.5 in those without distant metastases (p=0.002 and p=0.001, respectively). The median CA 19-9 and carcinoembryonic antigen (CEA) levels in patients with distant metastases were 31.34 and 9.20, respectively, whereas those without distant metastases were 11.55 and 2.26, respectively (p=0.011 and p=0.001, respectively).

In our study, no statistically significant difference was found in terms of HER-2 status, SUV_max, SUV_mean, MTV, TLG, distant metastasis, presence of lymph node metastasis, age, gender, tumor diameter, grade, and localization, and CEA levels in patients with gastric cancer. A statistically significant difference was found between HER-2 status and CA 19-9 levels. A statistically significant relationship was found between distant metastases in the ¹⁸F-FDG PET/CT examination and SUV_max, SUV_mean, age, CEA levels, and histopathologic diagnosis; however, the relationship between distant metastasis in the ¹⁸F-FDG PET/CT scan and MTV, TLG, tumor diameter, localization, and grade was not statistically significant.