Abstract 6117: Characterizing cancer patterns in Okinawan vs. mainland Japanese Americans: The Multiethnic Cohort
Authors: Streicher Samantha A. , Park Song-Yi , Chiang Charleston W. , Sheng Xin , Bogumil David , Conti David V. , Haiman Christopher A. , Wilkens Lynne R. , Marchand Loic Le 
Published: March 2024

Abstract
Differences in chronic disease rates have been documented in Japan between Okinawa and mainland Japan. Limited data exist on whether these differences are also present in Okinawans and mainland Japanese who have migrated to the US. We used genotyped genome-wide association study data from the Multiethnic Cohort Study (MEC) to identify Japanese Americans of Okinawan or mainland ancestral similarity, and to investigate these two groups for differences in baseline chronic disease risk factors and for incidence of the four most common cancers during follow-up after blood draw. Cancer cases were identified via linkage to state cancer registries. Principal component analysis followed by uniform manifold approximation and projection (UMAP) was run using 15,678 single nucleotide polymorphisms among the 24,484 MEC Japanese Americans with blood samples. The Okinawan cluster was confirmed by labeling male MEC participants with Okinawan surnames on UMAP plots. Hazard ratios (HR), 95% confidence intervals (CI), and two-sided p-values were reported for Cox proportional hazards models, comparing cancer incidence between Okinawan and mainland Japanese individuals. The Okinawan cluster included 3,649 individuals (15% of the MEC Japanese Americans) and the mainland Japanese cluster included 19,611 individuals (80% of the MEC Japanese Americans). Small clusters of part-Okinawan and/or part-mainland Japanese (5% of the MEC Japanese Americans) were not included in the analysis. Ninety-six percent of Okinawan Americans and 94% of mainland Japanese Americans in MEC were born in the US. Okinawans were more likely to have a higher body mass index and daily alcohol intake, and less likely to be a current or former smoker, compared to mainland Japanese (all p-values&lt;0.05). Post-menopausal Okinawan women were significantly more likely to be diagnosed with breast cancer (age-adjusted HR=1.39, 95% CI=1.10-1.75) compared to post-menopausal mainland Japanese women. This association was not modified by adjusting for additional known breast cancer risk factors (HR=1.36, 95% CI=1.07-1.73). Okinawans were also less likely to be diagnosed with lung cancer (HR=0.75, 95% CI=0.58-0.98); however, this association was no longer significant when adjusting for known risk factors, including smoking history (HR=0.82, 95% CI=0.62-1.07). There were no significant differences in risk of colorectal or prostate cancer between Okinawan and mainland Japanese individuals. Our results in this US-based sample are consistent with recent trends of higher breast cancer and lower lung cancer age-adjusted incidence rates reported from Japan for the Okinawan prefecture compared to mainland prefectures. Investigating reasons for the observed breast cancer risk difference may identify new risk factors for this disease in the Okinawan and other populations.
Citation Format: Samantha A. Streicher, Song-Yi Park, Charleston W. Chiang, Xin Sheng, David Bogumil, David V. Conti, Christopher A. Haiman, Lynne R. Wilkens, Loic Le Marchand. Characterizing cancer patterns in Okinawan vs. mainland Japanese Americans: The Multiethnic Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6117.