Introduction
Colorectal cancer (CRC) is the third most common cancer in the United States and the third leading cause of cancer death. In aggregate, Asian Americans and Pacific Islanders (AAPI) have the lowest incidence rates of CRC among racial groups in the United States, as well as one of the highest 5-year survival rates. However, there is great heterogeneity among those who identify as AAPI that can be easily overlooked when this group is aggregated into a single category, potentially obscuring disparities in CRC incidence between subpopulations. Here, we examined trends and differences in CRC incidence rates in census AAPI subgroups from 1990 to 2014.

Methods
We used the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Registry to conduct a retrospective analysis of CRC incidence from 1990-2014 in detailed AAPI subpopulations compared to the non-Hispanic White population. SEER detailed AAPI data is available for 11 ethnic groups. We combined data sets for certain groups due to the small absolute number of cases represented by the SEER database: a group consisting of Vietnamese, Laotian, and Kampucheans, and another group of Guamanian/Chamorro and Samoans. Overall incidence is reported per 100,000 person-years and annual percental change (APC) was calculated with 95% confidence intervals (95% CI).

Results
From 1990-2014, CRC incidence was highest in Japanese, non-Hispanic Whites, and Hawaiian subpopulations (Table 1). Incidence decreased over the study period in these groups as well as in Chinese and Filipinos. Incidence increased in the Vietnamese, Laotian, Kampucheans, and Guamanian/Chamorro, Samoan groups. Early stage (stage 0-II) CRC incidence decreased in all groups evaluated. However, while incidence of late stage (stage III-IV) cancers decreased in non-Hispanic Whites, incidence increased in Korean, Asian Indian/Pakistani, Vietnamese, Laotian, Kampuchean, and Guamanian/Chamorro, Samoans. In the <50 years age group, CRC incidence increased in non-Hispanic Whites but decreased in Chinese and Koreans.

Conclusion
There was a great degree of heterogeneity in CRC incidence among the AAPI subpopulations in the United States from 1990-2014. While AAPI CRC incidence is generally lower than non-Hispanic Whites, Japanese and Hawaiian subpopulations have similar CRC incidence as non-Hispanic Whites. In addition, CRC incidence in individuals aged 50+ generally decreased in several AAPI subpopulations; however, differing trends in incidence for age <50 were seen. These results highlight the need for targeted and culturally appropriate CRC screening efforts for specific AAPI subpopulations at higher CRC risk.

There is heterogeneity in CRC incidence among AAPI subpopulations. SEER registry data in detailed AAPI groups was used in a retrospective analysis of CRC incidence from 1990-2014. Incidence is reported per 100,000 person-years and APC was calculated with 95% confidence intervals.

Vicki Tang

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