Among some of the startling statistics: The risk of developing anal cancer was five times higher for black men born in the mid-1980s compared to those born in the mid-1940s. That may be because young black men are disproportionately affected by HIV, which raises the risk for developing the cancer, Deshmukh said.
The risk doubled among white men and white women born after 1960. The disease may surpass cervical cancer to become the leading human papillomavirus-linked cancer in elderly women, the study noted. One possible reason: Older people have weaker immune systems, impairing their ability to clear HPV from their bodies, and elderly women outnumber elderly men.
The proportion of cases diagnosed when the cancer had already spread to other parts of the body doubled, which suggests the rise in cases isn’t driven by more intense screening that would catch early-stage tumors, Deshmukh noted.
“It’s really hard to understand what might be causing the rise in incidence and mortality,” he added. Possible reasons include a shift in sexual behaviors in recent decades, including normalization of anal sex and more sexual partners, and the rise in obesity rates, which could be a factor, he said.
For the study, published in the Journal of the National Cancer Institute, researchers analyzed data in U.S. cancer registries from 2001 through 2015. They also looked at causes of death from a database compiled by the National Center for Health Statistics over that time.