Study Finds Long-Term HRT Use Ups Breast Cancer Risk

A new study has found that normal weight women on hormone replacement therapy (HRT) and those who take combination estrogen/progestin therapy (EPT) over a longer time may face a higher risk of breast cancer, according to a report posted on WebMD. EPT drugs include <"">Prempro and <"">Premphase.

According to the journal Cancer Epidemiology, Biomarkers & Prevention, the study results—“HRT and Breast Cancer Risk: Study Details”—indicated that while it is widely known that EPT does increase breast cancer risks, what remains unknown are the response of different combinations, which women are high risk, and if risk changes based on tumor sub-type. The team looked at HRT and breast cancer risks using the California Teachers Study cohort, said Cancer Epidemiology, Biomarkers & Prevention and, after a 9.8-year mean follow-up, “2,857 invasive breast cancers were diagnosed.”

The group compared women who never took HRT to women who said they were on estrogen therapy (ET) for no less than 15 years and found that those women on long-term ET experienced a 19-percent increased risk of breast cancer, said Cancer Epidemiology, Biomarkers & Prevention. When the timing increased (15 years or more), the risk increased (83 percent), with the greatest risk seen in women using continuous combined EPT therapies. The team concluded that the findings call for more “personalized risk-benefit discussions with women contemplating HT (hormone therapy) use.”

In addition to considering HRT by type—estrogen alone or an estrogen/progestin combination—and length of regimen, the team looked at the women’s body mass index, or BMI, said WebMD. Progestin is key because it tells breast tissue to split, which can increase cancer risks, noted WebMD.

While women with a high BMI—30 or higher, considered obese—did not experience an increased breast cancer risk, women with BMIs of 29.9 or lower did, despite that obesity on its own is a breast cancer risk, wrote WebMD. Increased risks for breast cancer with HRT was linked to tumors positive for estrogen and progesterone and HER2-positive, explained WebMD.

The American Congress of Obstetricians and Gynecologists said that women should take the smallest dose of HRT for the shortest time frame, WebMD noted.

The report also noted that one study co-author—Christina A. Clarke—served as an expert plaintiff witness in a lawsuit over Prempro hormone therapy.

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