Abstract C82: Stomach cancer incidence trends among 10 racial/ethnic groups in California, 1988-2010
Authors: Liu Lihua , Barzi Afsaneh , Zhang Juanjuan , Deapen Dennis , Stern Mariana 
Published: May 2015

Background: Stomach cancer is characterized by marked disparities in incidence rates across regions and cultures of the world. Majority of stomach cancer cases occur in developing countries, especially in Asia. As the number of immigrants from Asia and Latin America continue to grow, particularly in places like California, come the unique research opportunities with the large and diverse populations to better understand and reduce the burden of stomach cancer. Analyzing stomach cancer incidence rates and trends by disaggregated individual racial/ethnic groups will facilitate the understanding of the disease, identify target population for intervention, and generate etiologic hypothesis.

Materials and Methods: Using data from the California Cancer Registry (CCR) and the decennial population census, we calculated the age-adjusted and age-specific incidence rates (AAIR and ASIR) of invasive stomach cancer over 5 time periods during 1988-2010 (1988-1992, 1993-1997, 1998-2002, 2003-2007, and 2008-2010) among 10 racial/ethnic population groups in California (Non-Hispanic White (NHW), Black, Hispanic, Chinese, Filipino, Korean, Japanese, Vietnamese, Asian Indian and Pakistani (South Asian), and a combined group of Laotian/Hmong/Cambodian/Thai (LHCT)). A total of 57,729 invasive stomach cancer cases were included in the study. Average annual percent change (AAPC) of AAIR and ASIR trends were calculated to quantify the rate changes over time. M:F ratios of AAIR by race/ethnicity were also examined.

Results: Koreans men and women had the highest AAIR and ASIR across time period and age group. Their rates were substantially higher than the rest of the population groups. Despite the dramatic decline of AAIR among Korean men from 62.8/100,000 in 1988-1992 to 37.1/100,000 in 2008-2010, it was still 2.2 times of that of the Japanese men (17.2/100,000), 4.7 times of NHW men (7.9/100,000), and 8.7 times of South Asian men (4.3/100,000). AAIR for Korean women dropped from its highest of 29.1/100,000 in 1993-1997 to its lowest of 21.1/100,000 in 2008-2010 and remained twice as that of Japanese women (11.6/100,000). NHWs, Filipinos, and South Asians displayed consistently the lowest risk for developing stomach cancer.

During 1988-2010, stomach cancer AAIR declined for all sex-racial/ethnic groups, except South Asian women. The decline was more substantial among Vietnamese (AAPC -4.8 in men and -4.5 in women), Japanese (AAPC -3.8 in men and -3.3 in women), and Korean (AAPC -2.5 in men and -0.8 in women).

The M:F ratio of AAIR was highest among NHWs (2.2), the rest of the groups ranged from 1.8 in Hispanics, blacks, Filipinos, and Koreans to 1.1 in South Asians, during 2008-2010.

Analysis of ASIR showed that people aged 65 years and over had substantially higher incidence rates regardless of sex and race/ethnicity. The decrease in incidence trends was also often larger among older than younger people, and with specific racial/ethnic variations.

Conclusions: With disaggregated sub-Asian grouping, our analysis revealed the varied patterns in stomach cancer incidence rates and trends by sex, age, and specific race/ethnicity. These findings underline the need for further examining stomach cancer statistics among the diverse population groups, including immigrants and their descendants, in order to identify etiologic clues and develop more effective interventions.

Citation Format: Lihua Liu, Afsaneh Barzi, Juanjuan Zhang, Dennis Deapen, Mariana Stern. Stomach cancer incidence trends among 10 racial/ethnic groups in California, 1988-2010. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C82. doi:10.1158/1538-7755.DISP13-C82