New research suggests that long-term use of any type of hormones to ease menopause symptoms can raise a woman’s risk of breast cancer.
It is already known that taking pills that combine estrogen and progestin - the most common type of hormone therapy - can increase breast cancer risk. But women who no longer have a uterus can take estrogen alone, which was thought to be safe and possibly even slightly beneficial in terms of cancer risk.
The new study suggests otherwise, if the pills are used for many years. It tracked the health of about 60,000 nurses and found that use of any kind of hormones for 10 years or more slightly raised the chances of developing breast cancer.
“There’s a continued increase in risk with longer durations of use, and there does not appear to be a plateau,’’ said study leader Dr. Wendy Chen of Brigham and Women’s Hospital in Boston.
The hormone picture has been confusing, and the absolute risk of breast cancer for any woman taking hormone pills remains small. Doctors say women should use the lowest dose needed for the shortest time possible.
“It’s hard to be surprised that if you keep taking it, sooner or later it’s going to raise risk,’’ said Dr. Robert Clarke of Georgetown University’s Lombardi Comprehensive Cancer Center.
The study was discussed Sunday in Chicago at a conference of the American Association for Cancer Research.
Another study presented at the conference might help explain why black women are so much more likely than whites to develop and die from cervical cancer: They seem to have more trouble clearing HPV, the virus that causes the disease.
Doctors have long thought that less access to screening and follow-up health care were the reasons black women are 40 percent more likely to develop cervical cancer and twice as likely to die from it. The new study involving young college women suggests there might be a biological explanation for the racial disparity, too.
If further study confirms this novel finding, it would make the HPV vaccine even more important for black women, said Worta McCaskill-Stevens, a prevention specialist at the National Cancer Institute. The vaccine is recommended for all girls starting at age 11.
Certain strains of HPV, the human papillomavirus, cause cervical cancer, but brief infections are very common in young women. They usually go away on their own within a year or so and only pose a cancer risk when they last long-term.
Researchers at the University of South Carolina in Columbia studied 326 white and 113 black students taking part in a wider federal health study. All were given Pap tests - lab exams of cells scraped from the cervix - and HPV tests every six months throughout their years in school.
Although the groups were similar in how many new HPV infections were detected and risk factors such as how many sex partners they had, doctors saw striking differences in how long their infections lasted.
At any checkup, black women were 1.5 times more likely to test positive for infection with one of the HPV strains that raise cancer risk, said study leader Kim Creek.
“The African-American women weren’t clearing the virus as fast,’’ he said. “They were actually holding onto it about six months longer,’’ for 18 months versus 12 months for white women. Ten percent of black women had abnormal Pap tests versus 6 percent of whites.
Two years after initial infections were found, 56 percent of black women were still infected but only 24 percent of white women remained infected.
The government’s National Institute on Minority Health and Health Disparities sponsored the study.