There's been a steep uptick in aggressive uterine cancers among American women, especially black women, since 2000, a new study shows.
It also found that black women with these aggressive cancers have lower survival rates than other women.
Researchers at the U.S. National Cancer Institute analyzed data on uterine cancer among 30- to 79-year-olds. They found that cases rose roughly 1 percent a year from 2003 to 2015.
Rates among black women surpassed those for white women in 2007 and were consistently higher from 2011 through 2015.
The researchers also took a closer look at endometrioid and non-endometrioid subtypes of uterine cancer. Endometrioid cancers start in the uterine lining, or endometrium. They are more common, usually have better outcomes and survival rates, and are more strongly linked with hormonal risk factors and obesity. Non-endometrioid subtypes can begin in the other supporting tissues of the uterus, and are rarer.
Rates of endometrioid subtypes were stable in white women over the study period, but they increased among other racial/ethnic groups. Rates of aggressive non-endometrioid subtypes rose 2.9 percent a year from 2000 to 2015 in all racial/ethnic groups.
But black women had much higher rates of aggressive non-endometrioid uterine cancers (25.9 per 100,000) over the period than white women (11.4), Hispanic women (10.1), and Asian/Pacific Islander women (7.5).
The five-year relative survival rate was lower for all women with non-endometrioid subtypes than for endometrioid subtypes. Black women had the lowest survival rates, no matter the subtype or how far advanced their cancer was at diagnosis.
"All of these trends -- the rates of uterine cancer among black women exceeding those of white women, the higher incidence rates of non-endometrioid subtypes among black women, and the lower survival rates of black women for all uterine cancer -- are very concerning," said lead author Megan Clarke, a postdoctoral fellow in the division of cancer epidemiology and genetics at NCI.
"We need to continue research to further understand these racial differences and disparities, in order to help us better predict risk and work toward prevention," Clarke added in an institute news release.
She noted that aggressive, non-endometrioid cancers are increasing for all women, but because they're much rarer than endometrioid subtypes, less is known about them.
Clarke said the increasing incidence of non-endometrioid subtypes is probably not due to rising obesity among women or changes in the use of hormone replacement therapy. Those factors are more strongly associated with the endometrioid subtypes.
"If the increasing incidence rate was primarily related to obesity, we wouldn't see stable trends for endometrioid subtypes among white women," Clarke said. "Obesity is the strongest risk factor associated with endometrioid subtypes. However, our study suggests that there are other factors leading to the increases in incidence of uterine cancer, and this warrants further research." The study was published May 22 in the Journal of Clinical Oncology.
The U.S. Office on Women's Health has more about uterine cancer.
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