Hysterectomy-corrected uterine cancer incidence rates show racial disparities, rising subtypes
Incidence rates of aggressive uterine cancer subtypes have increased rapidly since the turn of the century, with racial disparities reflected in higher rates and shorter survival among black women, according to a study published in Journal of Clinical Oncology.
“Incidence rates of uterine cancer have been rising, and there have been previous reports of racial differences in incidence and survival rates, with disparities observed for non-Hispanic black women,” study author Megan Clarke, PhD, postdoctoral fellow in the NCI’s division of cancer epidemiology and genetics, said in a press release. “But few recent studies have corrected for hysterectomy, which can vary by race and ethnicity and by region. Correcting for hysterectomy prevalence gives us a more accurate picture of trends in overall incidence, as well as rates by race and ethnicity.”
Clarke and colleagues used the SEER database to obtain incidence data on all confirmed cases of invasive corpus uteri and uterine corpus not otherwise specified cancers diagnosed between 2000 and 2015. The study population included women of Hispanic and non-Hispanic (white, black and Asian Pacific Islander) race or ethnicity.
The researchers used the Behavioral Risk Factor Surveillance System to estimate rates of hysterectomy, and they calculated hysterectomy-corrected, age-standardized uterine corpus cancer rates from 18 population-based registries representing about 28% of the U.S. population. Researchers assessed incidence rates and trends separately based on ethnicity, religion and histologic subtype, and estimated 5-year relative survival by race/ethnicity, histologic subtype and disease stage.
Results showed that non-Hispanic whites and blacks had similar hysterectomy-corrected rates of uterine corpus cancer, whereas Hispanics and Asians/Pacific Islanders had lower rates. Hysterectomy rates among U.S. women decreased from 27.3% in 2000 to 23.9% in 2015. The overall prevalence of hysterectomy during this interval was 25.2%.
Non-Hispanic whites had the highest prevalence of endometrioid carcinoma, and non-Hispanic blacks had the highest rates of nonendometrioid carcinoma and sarcoma.
The researchers found that correction by hysterectomy had a noteworthy impact on patterns of uterine cancer. In the overall population, uncorrected incidence rates increased by about 1% (95% CI, 0.4-1.5) annually between 2000 and 2015. Hysterectomy correction decreased the average annual percentage change to 0.5 (95% CI, –0.1 to 1.1) for the entire period. However, corrected rates increased significantly between 2003 and 2015 (annual percentage change, 1.1%; 95% CI, 0.7-1.4).
of 3.3% (95% CI, 2.8-3.7) annually. Corrected rates showed a 2.9% (95% CI, 2.4-3.4) increase per year.
Hysterectomy-corrected uterine corpus cancer incidence rates rose among non-Hispanic blacks, Hispanics and Asians/Pacific Islanders between 2000 and 2015. In 2007, overall incidence rates among non-Hispanic blacks exceeded those of non-Hispanic whites and were repeatedly higher from 2011 to 2015. Endometrioid carcinoma rates increased among non-Hispanic blacks, Hispanics and Asians/Pacific Islanders, but not among non-Hispanic whites.
Rates of nonendometrioid carcinoma increased among women of all races and ethnicities, including 2.3% (95% CI, 1-3.7) among whites, 3.2% (95% CI, 2.5-4) among blacks, 3.8% (95% CI, 2.8-4.9) among Hispanics, and 4.4% (95% CI, 3.1-5.6) among Asians/Pacific Islanders. Non-Hispanic blacks demonstrated the lowest rates of survival, independent of disease stage or histologic subtype.
The researchers also evaluated age-adjusted incidence rates of uterine cancer. The overall hysterectomy-corrected incidence rate was 63.7 per 100,000 woman-years, which was 59% higher than the uncorrected rate of 40 per 100,000 woman-years.
The pronounced increases in nonendometrioid aggressive subtypes of uterine cancer cannot be attributed to obesity, which is often cited as a factor in uterine cancer increases, according to a related editorial by Megan A. Mullins, MPH, doctoral student at University of Michigan School of Public Health, and Michelle L. Cole, MPH, PhD, associate professor at Wayne State University School of Medicine and assistant center director for education at Karmanos Cancer Institute in Detroit.
“In this regard, although excess unpposed estrogen in obese women is a strong risk factor for the development of low-grade endometrioid endometrial cancers, it may play less of a role in the nonendometrioid aggressive subtypes,” the authors wrote. “Given the older median age at diagnosis of nonendometrioid cancers, this increase likely reflects differences in women born on the cusp of the baby boomer generation compared with women who are squarely baby boomers.” – by Jennifer Byrne
Disclosures: Clarke reports stock in Johnson & Johnson and Merck. Please see the study for all other authors’ relevant financial disclosures. Mullins reports a consultant/advisory role with EpidStat Institute. Cole reports no relevant financial disclosures.