Background: Endometrial cancer incidence is lower but mortality is higher among black relative to white women. This disparity results from a relatively higher level of case-fatality in African Americans. We investigated whether the inter-racial difference in survival has diminished in more recent birth cohorts.
Methods: Women diagnosed with endometrial malignancies during 1977–1996 were identified from the U.S. Surveillance, Epidemiology and End Results program (45,261 white and 1986 black women). We calculated cumulative 5-year relative survival for 6 birth cohorts.
Results: Survival was relatively higher in younger women than older women and in women diagnosed in earlier years compared with more recent years. Higher survival was evident in more recent birth cohorts for groups of women 60+ years of age and in all time periods, particularly for black women.
Conclusions: Although black women with endometrial cancer have a poorer prognosis than white women, the inter-racial difference in survival has narrowed in more recent birth cohorts.
From the *Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada; †Division of Population Health and Information, Alberta Cancer Board, Calgary, Alberta, Canada; ‡Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada; §Department of Oncology, University of Calgary, Calgary, Alberta, Canada; ¶Division of Public Health Services, Fred Hutchinson Cancer Research Center, Seattle, Washington; and ∥Department of Epidemiology, University of Washington, Seattle, Washington.
Submitted 27 October 2005; accepted 3 February 2006.
Supported by the Peter Lougheed New Investigator Research Award (awarded to LSC), Canadian Institutes of Health Research.
Correspondence: Linda S. Cook, Department of Community Health Sciences, University of Calgary, 3330 Hospital Drive N. W., Calgary, AB T2N 4N1 Canada. E-mail: firstname.lastname@example.org.
Age-adjusted endometrial cancer incidence among white women in the United States is twice that of black women, yet age-adjusted mortality from uterine cancer among black women is twice that of white women.1–21 Mortality rates have decreased for both black and white women over the last 25 years,22 but inferences regarding possible trends in inter-racial survival are hindered by racial differences in incidence trends during this period. We sought to determine whether there has been an improvement in relative survival for blacks diagnosed with endometrial cancer in more recent birth cohorts beyond that experienced by whites.
Data were from 9 registries in the Surveillance, Epidemiology and End Results (SEER) Program.23 (See Table 1 footnote for complete list.) We identified women diagnosed with a first primary cancer of the uterine corpus or the uterus, not otherwise specified, between 1977 and 1996.23 Because follow-up data were available through the end of 2001, 1996 was the last diagnosis year to ensure a minimum 5-year follow-up period. Of the 53,225 white and 3182 black women identified, women were excluded based on the following criteria: diagnosis via autopsy/death certificate (n = 305 and n = 24, respectively); no microscopic confirmation (376 and 41); International Classification of Diseases for Oncology (ICD-O)24,25 site codes of C54.2 (myometrium) and C54.8 (overlapping lesion of the corpus uteri; 200 and 27); nonglandular histologies (4641 and 822); clear cell or serous adenocarcinoma histologies (because survival among women with these tumors is known to be lower than survival among women with more common endometrial adenocarcinomas; 366 and 196)19; age less than 40 years at diagnosis (1076 and 86).
Thus, the final analysis included 45,261 white and 1986 black women whose tumors were classified by ICD-O-3 codes of 8140–8143, 8200, 8210, 8260–8263, 8323, 8340, 8380, 8440, 8470, 8480, 8481, 8560, 8570, 8571, or 8573. Vital status 5 years after diagnosis was available for 99.2% of white and 98.9% of black women. Women lost to follow-up before 5 years were censored at the last known follow-up year.
Cumulative 5-year relative survival was calculated by comparing the ratio of the observed overall survival of the cases to the expected survival of women in the general population who were similar to the cases with respect to age, race and time period of diagnosis.22,23 All deaths, irrespective of cause, were included. The major advantage of relative survival in population-based studies is that cause of death information is not required. Relative survival provides a measure of excess mortality in endometrial cancer cases beyond that experienced by their counterparts in the general population.26 Relative survival by birth cohort also was examined by age group and by time period of diagnosis. The relatively small number of black women precluded simultaneous stratifications by birth cohort, age group at diagnosis and time period. Results for strata with fewer than 25 cases available for follow-up were not reported due to unstable survival estimates, nor were corresponding estimates in the other racial group.
During 1977–1996, 5-year relative survival was greater in younger than in older women (Table 1; Fig. 1), in more recent years than in earlier ones (Table 1; Figs. 2 and 3), and particularly in more recent birth cohorts (Table 1; Figs. 1 and 3). Relative survival improved in both black and white women over successive birth cohorts (29% to 79% for black and 63% to 95% for white women, P for both trends <0.001), but absolute improvement was more pronounced for black women (Table 1). The association of survival with birth cohort was evident in women 60 years of age and older (Fig. 1) and in all time periods (Fig. 3). The disparity in five-year relative survival between black and white women was substantially smaller in more recent birth cohorts than in earlier ones (Table 1; Figs. 1 and 3).
Although black women consistently experienced poorer survival relative to white women after a diagnosis of the most common forms of endometrial cancer, substantial absolute improvements in 5-year relative survival were noted for black women over successive birth cohorts beyond those experienced by white women.
Relative survival was better in younger women than in older women (Table 1). The earliest cohort (1880–1899) included a high proportion of women who were older at diagnosis, whereas the most recent cohort (1940–1956) included a high proportion who were younger at diagnosis. Thus, the higher relative survival among women in recent birth cohorts partially reflects the differing ages at diagnosis across birth cohorts. However, when we stratified the data by age at diagnosis (Fig. 1), we continued to see increases in survival for similarly aged women in more recent cohorts, at least among women 60 years of age and older.
Earlier detection, even without changes in the natural history of the disease, can lead to a calculated increase in survival despite no real improvement in prognosis.27 Although the SEER program does collect information on stage of disease at diagnosis, the likely incomparability of the assessment of stage between races especially over time, limits the usefulness of this information for identifying changes in stage at diagnosis that could influence prognosis. However, age-adjusted mortality from endometrial cancer has decreased for both black and white women over the time period of our study,22 suggesting that the increases in survival that we observed among women in recent birth cohorts are indicative of some additional lives having been saved in these women.
Prior studies have noted poorer survival after endometrial cancer among black women relative to white women, whether this was assessed by overall survival,5,7,11,18,19 relative survival,1,19,21 or cause-specific survival.3,17 In most studies that adjusted for various other factors such as age, disease stage, tumor grade/histology, treatment and income, survival differences diminished but were not eliminated,6,9,11,18,28 but in others race was no longer predictive of survival after such adjustments.12,15,16 To our knowledge, no other study has investigated endometrial cancer survival by birth cohort for white and black women.
In conclusion, our results indicate that relative survival is increasing over successive birth cohorts in black women diagnosed with the most common types of endometrial cancer. Nonetheless, a disparity in survival between white and black women remains, and the basis for this disparity continues to be elusive.
1. Axtell LM, Myers MH. Contrasts in survival of black and white cancer patients, 1960–73. J Natl Cancer Inst
2. Aziz H, Hussain F, Edelman S, et al. Age and race as prognostic factors in endometrial carcinoma. Am J Clin Oncol
3. Bain RP, Greenberg RS, Chung KC. Racial differences in survival of women with endometrial cancer. Am J Obstet Gynecol
4. Beckner ME, Mori T, Silverberg SG. Endometrial carcinoma: nontumor factors in prognosis. Int J Gynecol Pathol
5. Christopherson WM, Connelly PJ, Alberhasky RC. Carcinoma of the endometrium. V. An analysis of prognosticators in patients with favorable subtypes and Stage I disease. Cancer
6. Connell PP, Rotmensch J, Waggoner SE, et al. Race and clinical outcome in endometrial carcinoma. Obstet Gynecol
7. Connelly PJ, Alberhasky RC, Christopherson WM. Carcinoma of the endometrium. III. Analysis of 865 cases of adenocarcinoma and adenoacanthoma. Obstet Gynecol
8. Cronje HS, Fourie S, Doman MJ, et al. Racial differences in patients with adenocarcinoma of the endometrium. Int J Gynaecol Obstet
9. Hicks ML, Kim W, Abrams J, et al. Racial differences in surgically staged patients with endometrial cancer. J Natl Med Assoc
10. Hicks ML, Phillips JL, Parham G, et al. The National Cancer Data Base report on endometrial carcinoma in African-American women. Cancer
11. Hill HA, Eley JW, Harlan LC, et al. Racial differences in endometrial cancer survival: the black/white cancer survival study. Obstet Gynecol
12. Kost ER, Hall KL, Hines JF, et al. Asian-Pacific Islander race independently predicts poor outcome in patients with endometrial cancer. Gynecol Oncol
13. Larson DM, Copeland LJ, Gallager HS, et al. Prognostic factors in stage II endometrial carcinoma. Cancer
14. Madison T, Schottenfeld D, Baker V. Cancer of the corpus uteri in white and black women in Michigan, 1985–1994: an analysis of trends in incidence and mortality and their relation to histologic subtype and stage. Cancer
15. Matthews RP, Hutchinson-Colas J, Maiman M, et al. Papillary serous and clear cell type lead to poor prognosis of endometrial carcinoma in black women. Gynecol Oncol
16. Morgan MA, Behbakht K, Benjamin I, et al. Racial differences in survival from gynecologic cancer. Obstet Gynecol
17. Ragland KE, Selvin S, Merrill DW. Black-white differences in stage-specific cancer survival: analysis of seven selected sites. Am J Epidemiol
18. Randall TC, Armstrong K. Differences in treatment and outcome between African-American and white women with endometrial cancer. J Clin Oncol
19. Sherman ME, Devesa SS. Analysis of racial differences in incidence, survival, and mortality for malignant tumors of the uterine corpus. Cancer
20. Steinhorn SC, Myers MH, Hankey BF, et al. Factors associated with survival differences between black women and white women with cancer of the uterine corpus. Am J Epidemiol
21. Young JL Jr, Ries LG, Pollack ES Cancer patient survival among ethnic groups in the United States. J Natl Cancer Inst
22. Surveillance, Epidemiology, and End Results (SEER) Program. SEER*Stat Database: Mortality - All COD, Public-Use With State, Total U.S. (1969–2001), National Cancer Institute, DCCPS, Surveillance Research Program, Cancer Statistics Branch, released April 2004. Underlying mortality data provided by NCHS (www.cdc.gov/nchs
). Available at: www.seer.cancer.gov
23. Surveillance, Epidemiology, and End Results (SEER) Program. SEER*Stat Database: Incidence - SEER 9 Regs Public-Use, Nov 2003 Sub (1973–2001), National Cancer Institute, DCCPS, Surveillance Research Program, Cancer Statistics Branch, released April 2004, based on the November 2003 submission. Available at: www.seer.cancer.gov
24. Fritz A, Percy C, Jack A, et al. International Classification of Diseases for Oncology
. 3rd ed. Geneva: World Health Organization; 2000.
25. Percy C, Van Holten V, Muir C. International Classification of Diseases for Oncology
. 2nd ed. Geneva: World Health Organization; 1990.
26. Dickman PW, Sloggett A, Hills M, et al. Regression models for relative survival. Stat Med
27. Welch HG, Schwartz LM, Woloshin S. Are increasing 5-year survival rates evidence of success against cancer? JAMA
28. Madison T, Schottenfeld D, James SA, et al. Endometrial cancer: socioeconomic status and racial/ethnic differences in stage at diagnosis, treatment, and survival. Am J Public Health