Study

Menopausal Hormone Therapy Increases Risk of Breast Cancer

As little as three years of using combined estrogen and progestin menopausal hormone therapy substantially increases the risk of developing lobular breast carcinoma, the results of new research indicate. "Previous studies suggest that only women who use these hormones for at least five years have an increase in breast cancer risk, but none have evaluated how shorter durations of use impact risk of lobular breast cancer," lead author Dr Christopher I Li said.

Lobular breast cancers affect the many small sections (the lobules) that end in dozens of tiny bulbs that produce milk. Ductal breast cancers form in the thin tubes that link together the lobes, lobules, and bulbs of the breast. Li, from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues note that invasive ductal carcinoma is still the most common type of breast cancer in the US (about 70 per cent of cases), but invasive lobular and mixed ductal-lobular carcinomas now make up about 16 per cent of cases.

As they report in the journal Cancer Epidemiology, Biomarkers, and Prevention, the researchers conducted a population-based study that included 324 women with lobular, 524 with ductal, and 196 subjects with ductal lobular breast cancer who were diagnosed between 2000 and 2004. A comparison group consisted of 469 women who were randomly picked from the general population.

Women who were currently on combination hormone therapy had an increased risk of lobular and ductal lobular carcinoma of 2.7 and 3.3-fold, respectively. At least three years of treatment with combined hormone therapy was needed to see an increased risk. Further analysis showed that combined hormone therapy only increased the risk for ductal lobular carcinomas that were dominated by lobular tissue.

"Overall, I do not think that these findings substantially change current recommendations regarding use of hormone therapy. Women considering hormone use should still try and use hormones for the shortest time possible and should use the lowest dose possible," Li said.

Reuters Health