Evaluation of Human Epidermal Growth Factor Receptor 2 Expression in Gastric and Gastroesophageal Cancers in Tanzania

Context.-The incidence of human epidermal growth factor receptor 2 (HER2) positivity in gastric cancers differs widely across various populations and is unknown in many low-resource settings. Objective.-To evaluate the rates of HER2 positivity in gastric and gastroesophageal adenocarcinoma at a national referral hospital in East Africa. We also assessed the association between HER2 overexpression and patient clinicopathologic characteristics. Design.-A retrospective review of cases diagnosed as either gastric or gastroesophageal adenocarcinoma between 2013 and 2017 was performed at Muhimbili National Hospital in Dar es Salaam, Tanzania. Of 1205 specimens meeting inclusion criteria, stratified random sampling was conducted to select 150 cases for HER2 immunohistochemistry and clinicopathologic analysis. Results.-The median age of patients was 56.5 years, with 65.3% (98 of 150) of the cohort composed of male patients, and 34.7% (52 of 150) of female patients. HER2 overexpression was identified in 6.0% (9 of 150) of cases. Approximately half of the tumors (51.3%; 77 of 150) were intestinal-type gastric adenocarcinoma, and 36.0% (54 of 150) were moderately differentiated. Intestinal-type (P =.01) and well-differentiated tumors (P =.001) were associated with HER2 overexpression. Conclusions.-HER2 overexpression was primarily seen in intestinal-type and well-differentiated tumors. Therefore, prioritizing HER2 testing for patients with intestinaltype, well- differentiated, or moderately differentiated gastric and gastroesophageal adenocarcinomas may be appropriate in Tanzania in efforts to allocate testing for patients who are most likely to benefit from trastuzumab therapy.