br Introduction br Ovarian cancer is the most

1. Introduction
Ovarian cancer is the most fatal cancer of the female reproductive system, but its etiology is still poorly understood. Worldwide, ovarian cancer incidence rates are higher in Europe and North America than in Asia and Africa [1]. This may be attributable to distinct differences in ovarian cancer histotype, risk factors, and biomarkers, which have been observed between Asian women and women of European descent [2,3]. Variation in ovarian cancer incidence rates by country has also been noted within regions of the world; for example, the incidence rate in Japan is more than twice that of China [1,4,5].
There has been a growing body of literature highlighting the het-erogeneity in the Asian ITF2357 and the need to disaggregate the Asian ethnic groups to better understand cancer burden and develop
more targeted and effective cancer control measures [6–12]. However, thus far, ovarian cancer research in the United States (U.S.) has re-garded Asian Americans as a single aggregated group, which may have likely masked important ethnic-specific differences for generating new research hypotheses and identifying high-risk groups.
Hence, in the following, we present our study of subgroup differ-ences in ovarian cancer incidence rates among the six largest Asian American ethnic groups: Asian Indian/Pakistani, Chinese, Filipino, Japanese, Korean, and Vietnamese. While it has been well-established that Asian American women as a single group have a lower rate of ovarian cancer incidence relative to non-Hispanic white (NHW) women based on findings from previous studies, we hypothesize that the rate of incidence may vary when each Asian American ethnicity is considered separately.
Abbreviations: U.S., United States; NHW, non-Hispanic white; NOS, not otherwise specified; AAIR, age-adjusted incidence rate; IRR, incidence rate ratio; AAPC, average annual percent change; SEER, Surveillance, Epidemiology, and End Results; ASIR, age-specific incidence rate; CI, confidence interval Corresponding author at: 800 N. State College Blvd, KHS 127, Fullerton, CA 92831, United States. E-mail address: alicelee@fullerton.edu (A.W. Lee).
2. Methods
2.1. Cancer case identification
Data from the National Cancer Institute’s SEER database November 2016 submission [13] were used in this analysis. All data were de-identified and coded for public use, thus this study was exempt from Institutional Review Board review. A total of 13 population-based cancer registries were included (Atlanta (metropolitan), Connecticut, Detroit (metropolitan), Hawaii, Iowa, New Mexico, Utah, New Jersey, Seattle-Puget Sound, San Francisco/Oakland, San Jose/Monterey, Los Angeles, and all remaining areas in California) representing 54% of the U.S. Asian and Pacific Islander population [14].
Cases classified as Asian Indian/Pakistani, Chinese, Filipino, Japanese, Korean, and Vietnamese were included, along with the NHW cases for comparison purposes. Asian Indians and Pakistanis were combined based on SEER coding rules for race.
2.2. Population estimates
To calculate the incidence rates, the annual at-risk population by age, sex, and ethnicity was estimated by the SEER program as described in previous publications [6,11]. Briefly, the population distributions by age, sex, and detailed/specific Asian ethnicity within the total Asian population from 1990, 2000, and 2010 Censuses of a given registry catchment area were used to disaggregate the Census Bureau’s annual population estimates of the total Asian American group for the same geographic area. Due to the multiracial identification method used in the 2000 and 2010 Censuses, estimates were based on the averages of the single-race and multi-race counts. The 1991 to 1999 and the 2001 to 2009 population estimates were developed from a linear interpola-tion between the 1990 and 2000 estimates and the 2000 and 2010 estimates, respectively. The 2011 to 2014 population estimates were developed from a linear extrapolation of the 2000–2010 growth trends. The annual population estimates for the NHW group came directly from the same Census Bureau estimation series.
2.3. Statistical analysis
Ovarian cancer patient demographic and tumor characteristics were compared across NHWs and all six Asian American ethnicities using Chi-square tests. Chi-square tests were also performed excluding NHWs to determine if such characteristics differed across the six Asian American ethnicities only. These analyses were performed using SAS software, release 9.4 (SAS Institute, Inc., Cary, North Carolina).
Distribution of demographic and tumor characteristics of ovarian cancer cases by race/ethnicity, 1990–2014.
Characteristic Non-Hispanic Asian Indian/ Chinese* Filipino* Japanese* Korean* Vietnamese* Chi-square P- Chi-square P-
White* Pakistani*