To the Editor We read with great interest the article by Chu et al1 that describes the association of proton pump inhibitors and capecitabine efficacy in advanced gastroesophageal cancer. We agree with the authors that there are limitations to the study. Furthermore, together in viewing the previous publication regarding the same population,2 we believe that the study raised an issue regarding the difference in response to treatment with anti–human epidermal growth factor receptor 2 (HER2) drugs among cancer patients of different ethnic groups.