Is the incidence of esophageal adenocarcinoma increasing in Japan? Trends from the data of a hospital-based registration system in Akita Prefecture, Japan

At present, squamous cell carcinoma accounts for most esophageal cancers in Japan; however, there is concern that the incidence of esophageal adenocarcinoma in Japan is increasing in comparison to Western countries. Akita Prefecture, with a population of 1 million, has the highest rate of esophageal cancer-associated mortality in Japan; the vast majority of these cases are squamous cell carcinoma. The aim of the present study was to investigate the latest trends in the incidence of esophageal adenocarcinoma in Akita Prefecture using a registration system. We examined the data from a collaborative hospital-based registration system for cancer patients. Eleven of the main hospitals in Akita Prefecture participate in this system, which covers 90% of the cancer cases in the region and which provides near population-based data. Using this registration system, we examined the sequential trends in the percentage of adenocarcinoma cases in relation to total esophageal cancer cases in Akita Prefecture from 2007 to 2014. In 2007–2014, a total of 2527 esophageal cancer patients were registered in the system. Among these, only 43 (1.8%) had adenocarcinoma. However, the number of adenocarcinoma patients gradually increased from 1 case in 2007 to 14 cases in 2014. Consequently, the percentage of adenocarcinoma cases showed a significant increase from 0.66% in the first 4 years of the study period to 2.5% in the latter 4 years of the study period (P