Researchers examined trends in anal cancer cases for about 15 years and identified about 69,000 cases of anal cancer and more than 12,000 deaths during that time.
"Our results from the dramatic increase in incidence among black millennials and white women, rising rates of distant disease, and increases in mortality rates in anal cancer are very important," said the study's lead author, Ashish A. Deshmukh, assistant professor at the UTHealth School of Public Health, said in a statement. "Given the historical belief that anal cancer is rare, it is often neglected."
Distant disease is when cancer has spread to other parts of the body.
From 2001 to 2015, cases of the most common type of anal cancer increased by 2.7% per year, while anal cancer death rates increased by 3.1% per year from 2001 to 2016.
The study, published in the Journal of the National Cancer Institute, "gives figures to a trend that seems to happen over the past decade," said Dr. Virginia Shaffer, a colorectal surgeon and associate professor at Emory University's Winship Cancer Institute. "In that sense, it gives us figures of what we already expected." Shaffer did not participate in the study.
Cancer associated with HPV
Anal cancer occurs where the digestive tract ends. It differs from colon or rectal cancers and most closely resemble cervical cancer.
The most common subtype of anal cancer is disc epithelial cancer, caused by human papillomavirus, known as HPV.
Who is affected by anal cancer?
The study found that cases of anal cancer have increased significantly in people 50 years and older.
Anal cancer is also rising among young black men.
The study also found that the number of cases in the advanced phase is increasing. This may be partly because the treatment for HIV has improved, Shaffer said, meaning patients live longer with compromised immune systems, and cancer may have developed further when diagnosed.
There is still stigma surrounding anal cancer.
"I know there are people who are ashamed," Cross told "CBS This Morning" in June. "You have cancer. Should you also feel that way ashamed that you did something bad because it lived in your anus? "
Anal cancer has become "quite taboo," Shaffer said. "I think because of some of the risk factors that have historically been known to be associated with it.
"If people have symptoms, they should see a doctor because I think many people think," Oh, it's just hemorrhoids "and can't control things, and it can also mean that you don't get diagnosed much, much later. "
To strengthen preventive efforts going forward, Shaffer said that all people eligible for vaccination should do so and that current vaccine guidelines should be studied to determine if they can be extended to other patients.
CNN's Michael Nedelman, Lisa Respers France and Sandee LaMotte contributed to this report.