Abstract PR03: Disaggregation of gastric cancer risk Between Asian American subgroups
Authors: Huang Robert J. , Hwang Joo Ha , Hsing Ann , Palaniappan Latha 
Published: September 2020

Introduction: Within the United States (US), Asian/Pacific Islanders (APIs) are at increased risk for non-cardia gastric adenocarcinoma (NCGA) compared to non-Hispanic whites (NHWs). Previous epidemiologic research has treated APIs as an aggregated group for analysis; however, substantial genetic and environmental differences may exist within subgroups. Very limited data exist regarding gastric cancer epidemiology as stratified by API subgroup.

Methods: All incident cases of NCGA diagnosed in the years 2000-2014 were identified from the Surveillance, Epidemiology, and End Results Program registries incorporating California, Connecticut, Detroit, Hawaii, Iowa, New Mexico, Seattle, Atlanta, and New Jersey. API subgroup of patients was identified: Korean, Japanese, Chinese, Vietnamese, Filipino, and Indian. API subgroup population estimates were obtained from the American Community Survey. The age-adjusted incidence rates per 100,000 population and 95% confidence intervals (CIs) were generated for each subgroup, and among non-Hispanic whites (NHWs) for reference. The stages of diagnosis (as defined by National Cancer Institute summary stage) were compared between subgroups. Differences between subgroups in all-cause mortality following diagnosis were evaluated utilizing proportional hazards (PH) regression, adjusting for differences in tumor stage, age, and gender.

Results: There exist substantial differences in age-adjusted incidences of NCGA between subgroups: Koreans (34.8 per 100K), Japanese (17.0 per 100K), Vietnamese (14.6 per 100K), Chinese (11.2 per 100K), Indian (5.4 per 100K), and Filipino (5.3 per 100K). The incidence among NHWs was 3.8 per 100K. All API subgroups as well as NHWs demonstrated a decrease in age-standardized incidence over the study period. There exist differences in the proportion of cancers diagnosed at local stage: Koreans (37.8%), Japanese (28.1%), Chinese (25.7%), Vietnamese (24.4%), Indian (21.6%), Filipino (18.9%), and NHWs (23.7%). API subgroups had better overall survival from NCGA compared to NHWs (reference) in PH regression: Korean (HR 0.50, CI 0.47-0.54, p&lt;0.001), Japanese (HR 0.79, CI 0.74-0.85, p&lt;0.001), Vietnamese (HR 0.79, CI 0.72-0.87, p&lt;0.001), Chinese (HR 0.70, CI 0.65-0.74, p&lt;0.001), and Indian (HR 0.69, CI 0.58-0.81, p&lt;0.001). These differences remained significant even after adjustment for stage of diagnosis, age, and gender.

Discussion: Substantial heterogeneity in risk for NCGA exist between API subgroups. Korean Americans are at highest risk, with incidence nearly seven-fold higher than Filipinos and Indians (whose risk is similar to NHW). This suggests that the higher NCGA-risk in APIs in aggregate are driven by certain subgroups. Interestingly, Koreans, Japanese, Vietnamese, Chinese, and Indians all had better survival following NCGA diagnosis than NHWs, even after adjustment for stage of diagnosis. These epidemiologic data may hold important implications for gastric cancer screening or surveillance programs.

This abstract is also being presented as Poster B104.

Citation Format: Robert J. Huang, Joo Ha Hwang, Ann Hsing, Latha Palaniappan. Disaggregation of gastric cancer risk Between Asian American subgroups [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr PR03.