Association between Salted Seafood Consumption and Biliary Tract Cancer in Patients Living in the Island Regions of Tokyo: Ecological Study Using Population-based Cancer Registry Data.

BACKGROUND

Although salted seafood is a known carcinogen for intestinal tract cancer, its effects on biliary tract cancer remain unclear. We examined salted seafood consumption's associations with biliary tract cancer on islands in Tokyo, where large salted seafood amounts are consumed.

METHODS

Due to the island region's small population, we applied age standardization using an indirect method based on Tokyo's population as the standard population. The standardized incidence ratio was calculated using Tokyo Metropolitan Cancer Registry data from 2013 to 2018. The salted seafood amount consumed was obtained from a nutritional survey conducted on the islands. Spearman's correlation coefficient was calculated between the salted seafood amount consumed and biliary tract cancer's incidence among the islands.

RESULTS

Six islands were included in this study (Oshima, Niijima, Kouzushima, Miyakejima, Hachijojima, and Ogasawara). The standardized incidence ratio was high in the islands (1.24). Of the six islands, Niijima (1.56) and Hachijojima (1.60) had high standardized incidence ratios, whereas Miyakejima (0.62) and Ogasawara (0.61) had low standardized incidence ratios. We found a positive correlation between the salted seafood amount consumed and biliary tract cancer's standardized incidence ratio (r=0.797, p=0.058).

CONCLUSION

Our ecological study suggests that salted seafood consumption may be a risk factor for biliary tract cancer. Further research, including animal studies and case-control studies conducted on the islands of Tokyo, is needed to clarify the association between salted seafood consumption and the incidence of biliary tract cancer.