Rates of Nonendometrioid Uterine Cancer Highest in Blacks

Veronica Hackethal, MD

May 30, 2019

Rates of uterine cancer have been increasing in the United States among all women, but particularly among racial/ethnic minorities, according to a study published online on May 22 in the Journal of Clinical Oncology.

Results suggest that the increase has been driven by increasing rates of nonendometrioid uterine cancer among racial/ethnic minorities. That is an aggressive subtype of uterine cancer for which survival is worse. Endometrioid tumors, the most common subtype of uterine cancer, are usually diagnosed early and are associated with a good prognosis.

The study also found that black women appear to be disproportionately affected. From 2000 to 2015, black women had the highest rates of nonendometrioid uterine cancer. They also had the lowest survival rates, regardless of stage at diagnosis or cancer subtype.

The study is the most comprehensive analysis of hysterectomy-corrected uterine cancer trends in the United States. In most prevous studies, analyses included women who had undergone hysterectomies. However, uterine cancer does not develop in women who have undergone hysterectomies, and not correcting for this factor can lead to an underestimation of uterine cancer rates.

The study is the first to evaluate hysterectomy-corrected uterine cancer trends among Hispanics and Asians.

"The rising incidence of nonendometrioid cancers poses a clinical challenge, as these subtypes present with more advanced stage at diagnosis and have worse survival compared to the more common endometrioid subtypes that clinicians are currently predominantly treating," author Megan Clarke, PhD, National Cancer Institute, Bethesda, Maryland, told Medscape Medical News via email.

"Increasing awareness among clinicians and patients regarding the signs and symptoms of uterine cancer, such as postmenopausal bleeding, and the differences in histologic subtypes among racial and ethnic groups may promote earlier diagnosis and timely referral to appropriate treatment," Clarke added.

Uterine cancer is the most common and the second deadliest gynecologic cancer in the United States. Although rates of uterine cancer are lower among black women, the cases that do occur are more likely to be aggressive, and mortality is higher for black women compared to white women. This racial disparity is one of the largest with respect to different cancer types.

To examine racial/ethnic differences in uterine cancer, researchers used data from the SEER database, which represents about 28% of the US population. Data also came from the Behavioral Risk Factor Surveillance System (BRFSS), the only nationally representative database that can be used to estimate hysterectomy prevalence. The analysis was adjusted for age, was corrected for hysterectomies, and included women who had been diagnosed with uterine cancer from 2000 to 2015. Owing to low numbers, the researchers excluded non-Hispanic American Indian/Alaska Native women and women of unknown race, as well as women younger than 30 years and older than 80 years.

From 2000 to 2015, the hysterectomy-corrected rates of uterine cancer were similar for white women and black women (for both, 67.6 per 100,000 woman-years; incidence rate ratio [IRR], 1.00; 95% confidence interval [CI], 0.99 – 1.01 for black women compared to white women). Rates were significantly lower among Hispanics (47.5 per 100,000 woman-years; IRR, 0.70; 95% CI, 0.70 – 0.71) and Asian/Pacific Islanders (40.0 per 100,000 woman-years; IRR, 0.59; 95% CI, 0.58 – 0.60).

Hysterectomy-corrected rates of uterine cancer in black women exceeded those in white women starting in 2007 and remained higher through 2015.uterine cancer in black women exceeded those in white women starting in 2007 and remained higher through 2015.

The highest rates of endometrioid cancer were among white women (52.6 per 100,000 person-years; IRR, reference), followed by blacks (34.5 per 100,000 person-years; IRR, 0.65; 95% CI, 0.65 – 0.66), Hispanics (33.7 per 100,000 woman-years; IRR, 0.64; 95% CI, 0.63 – 0.65), and Asian/Pacific Islanders (29.6 per 100,000 woman-years; IRR, 0.56; 95% CI, 0.56 – 0.57).

The highest rates of nonendometrioid cancer were among black women (25.9 per 100,000 woman-years; IRR, 2.27; 95% CI, 2.23 – 2.31]), followed by whites (11.4 per 100,000 woman-years; IRR, reference), Hispanics (10.1 per 100,000 woman-years; IRR, 0.89; 95% CI, 0.87 – 0.91), and Asian/Pacific Islanders (7.5 per 100,000 woman-years; IRR, 0.66; 95% CI, 0.64 – 0.68).

Overall, hysterectomy-corrected rates of uterine cancer rose significantly from 2003 to 2015 at 1.1% per year (95% CI, 0.7% – 1.4%).

From 2003 to 2015, hysterectomy-corrected rates of uterine cancer rose for all women, but the rate of increase was highest among Hispanic women (2.3% per year; 95% CI, 1.8% – 2.8%), followed by Asian/Pacific Islanders (2.2% per year; 95% CI, 1.7% – 2.7%), blacks (2.1% per year; 95% CI, 1.5% – 2.6%), and whites (0.8% per year; 95% CI, 0.4% – 1.2%).

Although hysterectomy-corrected rates of endometrioid cancer remained the same (0.0% per year; 95% CI, 20.7% – 0.6%), hysterectomy-corrected rates of nonendometrioid cancer rose significantly by 2.9% per year (95% CI, 2.4% – 3.4%).

The highest rates of endometrioid cancer were among white women. These rates remained the same over this time span (–0.2% per year; 95% CI, 20.9% – 0.5%).

In contrast, rates of endometrioid cancers increased among racial/ethnic minorities. The highest rate of increase was among Hispanic women (2.1% per year; 95% CI, 1.5% – 2.6%), followed by Asian/Pacific Islanders (1.8% per year; 95% CI, 1.4% – 2.3%) and blacks (1.3% per year; 95% CI, 0.7% – 2.0%).

Nonendometrioid cancer increased at the highest rates among Asian/Pacific Islanders (4.4% per year; 95% CI, 3.1% – 5.6%), followed by Hispanics (3.8% per year; 95% CI, 2.8% – 4.9%), blacks (3.2% per year; 95% CI, 2.5% – 4.0%), and whites (2.3% per year; 95% CI, 1.0% – 3.7%).

The lowest survival rates were among blacks, regardless of stage at diagnosis or type of uterine cancer. Overall 5-year survival for black women was 63.2%, compared to 86.1% for white women, 81.4% for Hispanic women, and 83.7% for Asian/Pacific Islanders.

The 5-year survival rate from nonendometrioid uterine cancer was 41.8% for black women, compared to 61.8% for white women, 57.5% for Hispanic women, and 59.7% for Asian/Pacific Islanders.

For nonendometrioid uterine cancer that had spread regionally, the rate of overall 5-year survival was 36% for black women, compared to 55.1% for white women, 50.1% for Hispanic women, and 56% for Asian/Pacific Islanders.

Why the Differences?

The reasons why black women are disproportionately affected by nonendometrioid uterine cancer and why they have lower survival rates are not well understood. The differences may be related to molecular and genetic factors. Disparities in medical care may also contribute, according to Clarke.

"We need to identify risk factors and exposures more specifically associated with nonendometrioid cancers to better understand the strong increases in this subtype among all women, and the particularly high rates and recent increases in non-Hispanic black women," she wrote.

"We also need to better understand the factors that contribute to the disparities in uterine cancer survival among non-Hispanic black women," she concluded.

The authors mentioned several limitations to the study. Data from the BRFSS and SEER databases do not completely capture all cases of uterine cancer, which could lead to an underestimation of uterine cancer rates. Also, the BRFSS only has data on hysterectomy for even-numbered years, so the researchers estimated hysterectomy prevalence for odd-numbered years.

The study was supported by grants from the National Cancer Institute and the National Institutes of Health. One or more authors report stock/other ownership interests or other relationship with one or more of the following companies: Merck, Johnson & Johnson, HCA Healthcare, Gilead Sciences, Celgene, Agilent, CVS Health, Encompass Healthcare, Roche, Becton Dickinson.

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J Clin Oncol. Published online May 22, 2019. Full text

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