Objective
The purpose of this study was to determine the association of type I endometrioid uterine cancer in US-born vs immigrant Asian women.
Study Design
Data were obtained from the Surveillance, Epidemiology, and End Results Program from 2001-2009. Chi-squared, Kaplan-Meier, and binomial logistic regression analyses were used for statistics.
Results
Of 4834 Asian women with uterine cancer, 62% were US-born and 38% were immigrants. Of these women, 2972 (61%) had type I (grade 1 or 2, endometrioid histologic type) uterine cancer. Compared with patients with type II disease (grade 3, clear cell and serous histologic type), patients with type I disease were younger (age 55 vs 59 years; P < .01) and had lower stage disease (90% vs 71%; P < .01). US-born Asian women had a significantly higher proportion of type I uterine cancers in contrast to their immigrant counterparts (65% vs 56%; P < .01). Of all immigrants, the proportion of type I cancers was lowest in Japanese women followed by Chinese and Filipino women, respectively (48% vs 52% vs 58%; P < .01). The 5-year disease-specific survivals of US-born vs immigrant Asian women with type I cancer was 92% for both groups. Over 3 time periods (2001-2003, 2004-2006, and 2007-2009), there was an increase in type I cancers among US-born Asian women (61% to 65% to 68%; P < .01).
Conclusion
US-born Asian women are more likely to be diagnosed with type I uterine cancer compared with immigrants. Over the study period, there was a trend towards an increase in type I cancers among US-born Asian women.
Uterine cancer is the most common gynecologic malignancy. In 2014, there were an estimated 52,630 new cases and an associated 8590 deaths. Approximately 7400 cases were diagnosed in Asian women. According to the US Census Bureau, the Asian population has grown by 3% per year, and a large majority were immigrants. Although a previous study from our group compared the survival of Asian women with white women with uterine cancer, there is limited information regarding the outcomes of subgroups of US-born and immigrant Asian women with this disease.
Type I uterine cancers are comprised primarily of low-grade (grades 1 and 2) endometrioid adenocarcinomas. These tumors are associated with unopposed estrogen stimulation and are influenced by diet and environmental exposures. Studies have shown that patients with type I uterine cancer are typically younger with a higher body mass index. Some authors have hypothesized that an Asian diet, as opposed to the high-caloric and fat Western diet, may contribute to lower rates of endometrial cancer and better survival. Conversely, patients with type II uterine cancer typically were seen at an older age, with higher grade tumor (grade 3), and aggressive histologic cell types (clear cell and serous histologic types). These tumors are often linked to genetic predisposition, predominantly serous carcinomas, and are associated with poorer prognosis.
The association between race and uterine cell types has been examined previously. Previous studies have shown that African American women are more likely to be diagnosed with poorer prognostic cell types compared with white women. Moreover, a previous report from our group demonstrated that Asian women were seen at a younger age and earlier stage, with favorable histologic condition, and have better survival vs white women. Migration status may also influence the types of cancer. For example, US-born Asian women have a higher incidence of breast, uterine, and ovarian cancer compared with their immigrant counterparts. Although the influence of migratory status has been explored, few reports have analyzed the difference among various Asian ethnic groups, particularly in relation to type I endometrioid uterine cancer. In this current study, we compared the proportion of type I uterine cancer in US-born vs immigrant Asian women and within various Asian ethnic groups.
Methods
Demographic, clinicopathologic, and treatment data from 2001-2009 were accessed on March 8, 2013, from the Surveillance, Epidemiology and End Results database of the United States National Cancer Institute. Because the Surveillance, Epidemiology and End Results database is a nationwide deidentified database, our study was not covered by an Institutional Review Board application. Data were reported from 9 population-based registries that comprise approximately 14% of the US population that includes Utah, Hawaii, Iowa, New Mexico, Connecticut, and Alaska and the metropolitan cities of Detroit (MI), San Francisco/Oakland (CA), Seattle (WA), Atlanta (GA), San Jose/Monterey (CA), and Los Angeles (CA). Similar to a previous report, we defined Asian race as Chinese, Filipino, Japanese, Korean, South-East Asian, and Indian. Given the small sample size of certain groups, we incorporated the Islander women with the Filipino women. We determined US birth status and Asian subgroups by using self-reported demographic information as previously described. We elected to define type I cancers as grade 1 or 2 endometrioid adenocarcinomas and type II as grade 3 endometrioid, clear cell, and serous histology based on the American Cancer Society designation.
Demographic, clinicopathologic, and treatment data, which included differences in age and stage of disease, were compared with the use of the chi-squared, t -test, and multivariate binomial logistic regression analysis. Survival analysis by age, stage, and migration status were performed with the use of Kaplan-Meier estimates. Factors in the multivariate model included age at diagnosis and birthplace (US-born vs immigrant). A 2-tailed probability value of < .05 was considered statistically significant. Statistical analyses were performed with R statistical software (version 2.15.2; R Foundation for Statistical Computation; Vienna, Austria).
Result
Of the 4834 women of Asian descent, the median age was 56 years (range, 19–96 years); the majority of the women (62%) were born in the United States ( Table 1 ). Filipino, Chinese, and Japanese patients comprised the largest ethnic groups at 48%, 16%, and 15%, respectively. Indian, South-East Asian, and Korean populations comprised the remainder of the women. Of patients with staging information, 64% of patients had stage I-II disease, and 12% had stage III-IV disease. Sixty-one percent of all patients were diagnosed with type I cancer, and the remaining 39% had type II cancers. Compared with patients with type II disease, patients with type I cancer were younger (age, 55 vs 59; P < .01) and had lower stage disease (90% vs 71%; P < .01). Proportionally, US-born women had a significantly higher proportion of type I uterine cancers in contrast to their immigrant counterparts (65% vs 56%; P < .01; Figure 1 ).
| Factor | Total (n = 4834) | Type I a (n = 2972) | Type II b (n = 1862) | P value |
|---|---|---|---|---|
| Age | < .01 | |||
| Median age, y (range) | 56 (19–96) | 55 (21–91) | 59 (19–96) | |
| Migratory status, n (%) | < .01 | |||
| US-born | 2974 (62) | 1936 (65) | 1038 (56) | |
| Immigrant | 1860 (38) | 1036 (35) | 824 (44) | |
| Ethnicity, n (%) | < .01 | |||
| Filipino | 2066 (48) | 1289 (62) | 777 (38) | |
| Chinese | 796 (16) | 462 (58) | 334 (42) | |
| Japanese | 721 (15) | 469 (65) | 252 (35) | |
| Southeast Asian | 295 (6) | 161 (55) | 134 (45) | |
| Indian | 283 (6) | 162 (57) | 121 (43) | |
| Korean | 167 (3) | 96 (57) | 71 (43) | |
| Stage, n (%) c | < .01 | |||
| I | 2758 (57) | 2145 (72) | 613 (33) | |
| II | 335 (7) | 222 (7) | 113 (6) | |
| III | 297 (6) | 144 (5) | 153 (8) | |
| IV | 287 (6) | 60 (2) | 227 (12) |
b Endometrioid grade 3, clear cell and serous carcinomas
c Stage of disease does not add up to 100% because 24% of the patients did not have staging information.
Asian subgroups with type I disease and migratory status are reported in Table 2 . We compared the proportion of type I uterine cancer within the various Asian ethnic groups. We found that Japanese, Chinese, and Filipino immigrants had lower proportions of type I uterine cancer (48% vs 52% vs 58%, respectively) compared with their US-born counterparts (68% vs 63% vs 66%; P < .01; Figure 2 ). The Filipino women reported only an 8% difference in proportion of type I cancers between US-born vs immigrants. Conversely, Japanese women showed a 20% difference in type I cancers between US-born and immigrant patients, which represented the largest difference within an ethnic group. In fact, Japanese immigrants showed the lowest proportion of type I cancer compared with other immigrant ethnic groups. In comparison to other US-born Asian women, the US-born Japanese women reported the highest proportion of type I uterine cancers of any group. Across all ethnic groups, US-born women had a higher proportion of type I cancers compared with their immigrant counterparts ( Table 2 ). On multivariate analysis, United States vs other birthplace (hazard ratio, 1.51; 95% confidence interval, 1.33–1.70; P < .01) and younger vs older age (hazard ratio, 1.95; 95% confidence interval, 1.73–2.20; P < .01) were independent predictors for higher proportion of type I uterine cancer ( Table 3 ). The 5-year disease-specific survival of Asian patients with type I vs type II disease was 92% vs 60%, respectively ( P < .01). Of type I cancer patients, younger age portended for better survival compared with older age (95% vs 87%; P < .01). Those with early-stage disease had a >5-year survival rate over advanced-stage cancers (94% vs 73%; P < .01). The survival rate of US-born vs immigrant Asian women with type I cancer was 92% for both groups ( Figure 3 ). Of note, migration status (US-born vs immigrant) was no longer a predictor for survival after adjustment for other demographic and clinicopathologic factors. Additionally, we investigated changes in the types of uterine cancer over 3 time periods (2001-2003, 2004-2006, and 2007-2009). The proportion of type I cancers did not vary over our study period (62% to 62% to 61%, respectively; P = .75) or with US Census Defined Divisions (West, 52%; Northeast, 62%; South, 56%; West, 62%; P = .26). We did not identify any significant change that was based on age at presentation (54 to 54 to 55 years, respectively; P = .09) but found a decrease in the proportion of advanced-stage disease (11% to 5% to 8%, respectively; P < .01). Over time, there was an increase in type I cancers among US-born women (61% to 65% to 68%, respectively; P <.01) and a decrease in type I cancers in their immigrant counterparts (39% to 35% to 32%, respectively; P < .01; Figure 4 ).
| Ethnicity | Proportion of type I cancer, n (%) | |||
|---|---|---|---|---|
| Total (n = 4834) | US-born (n = 1936) | Immigrants (n = 1036) | P value | |
| Filipino | 1289 (62) | 743 (66) | 546 (58) | < .01 |
| Chinese | 462 (58) | 278 (63) | 184 (51) | < .01 |
| Japanese | 469 (65) | 422 (67) | 47 (48) | < .01 |
| Southeast Asian a | 161 (55) | 100 (62) | 62 (51) | — |
| Indian a | 162 (57) | 62 (56) | 99 (53) | — |
| Korean a | 96 (57) | 36 (55) | 60 (59) | — |
| Predictor | Hazard ratio | Confidence interval | P value |
|---|---|---|---|
| Birthplace: United States vs other | 1.51 | 1.33–1.70 | < .01 |
| Younger age | 1.95 | 1.73–2.20 | < .01 |
