A new study adds more weight to the link between hormone use and breast cancer, although the evidence was circumstantial.
The study found the rate of two types of invasive breast cancer increased 65 percent from 1987-99. Researchers didn’t know how many of the 190,458 women age 30 and over took hormones, but the types of cancer that increased were those most strongly linked to hormone use.
The study appears in Wednesday’s Journal of the American Medical Association.
The two types of cancer that increased are lobular and lobular-ductal mixed. Those cancer types are often harder to spot from mammograms than the more typical ductal form of breast cancer.
So it would make more sense if there were an increase in ductal cancer, something that didn’t happen, said lead researcher Dr. Christopher Li of the Fred Hutchinson Cancer Research Center in Seattle.
Ductal cancer rates remained fairly stable during the study period, which was a time when an increasing number of women began taking the estrogen and progestin hormones, the researchers said.
The researchers ruled out other possible explanations for the prevalence increases, including rising use of mammography.
U.S. sales of Prempro, Wyeth Pharmaceuticals’ best-selling estrogen-progestin supplement, more than doubled from 1995-99 and more than tripled by 2001, surging to nearly $733 million, according to data from IMS Health.
But those sales fell significantly after the government last year halted its landmark study linking hormones with a slight increase in breast cancer.
That Women’s Health Initiative study prompted the Food and Drug Administration to approve new warning labels for hormone supplements for menopausal women. The labels note an increased risk for breast cancer and cardiovascular disease.
The JAMA research comes two days after release of more results from the government study, this time challenging the long-held belief that combined estrogen-progestin treatment improves memory and mental outlook.
Dr. Jay Brooks, a cancer specialist at Ochsner Clinic in Baton Rouge, La., said the JAMA study “adds to an increasing body of literature that now shows that the combined effects of estrogen-progesterone increases the risk of a woman developing breast cancer.”
“It’s a paradigm shift that’s been happening” as doctors increasingly recognize harm from treatments once thought to be beneficial to menopausal women, Brooks said.