Research shows that 5 or more years of combination (contains both estrogen and progesterone) hormone replacement therapy (HRT) increases breast cancer risk. Less is known about the risks of using HRT for fewer than 5 years. The study reviewed here showed that women using combination HRT for 3 or more years roughly tripled their risk of 2 types of breast cancer: invasive lobular carcinoma and mixed ductal-lobular carcinoma.
These breast cancers aren't seen as often as invasive ductal carcinoma, the most common type of breast cancer. There was more invasive ductal carcinoma in women who took combination HRT for more than 3 years compared to women who did not take HRT, but the increase wasn't statistically significant, which means it could have been due to chance.
The side effects of menopause dramatically reduce quality of life for some women. They have to weigh the benefits of HRT against the risks. If you're experiencing severe menopausal side effects and are considering HRT, talk to your doctor about how you can minimize your breast cancer risk. Estrogen-only HRT may be one option.
If you do decide to take HRT, try to use it for the shortest time possible. The study reviewed here found that breast cancer risk was not significantly increased when combination HRT was used for fewer than 3 years.
Together, you and your doctor can develop a plan to manage the side effects of menopause that is right for you.
NEW YORK (Reuters Health) - As little as 3 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 5 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 told Reuters Health.
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 percent of cases), but invasive lobular and mixed ductal-lobular carcinomas now make up about 16 percent 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 3 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.
Current combined hormone therapy use was associated with a 1.4-fold increased risk of ductal carcinoma, but this did not reach statistical significance.
"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.
As for further research, he commented, "The underlying biology explaining why hormones may impact the risk of certain types of breast cancer more strongly than other types remains poorly understood, so this is a problem we are actively studying."
"Also, now that various risks associated with hormone use have been identified, many women have started using other types of hormones, such as natural hormones, but very little is known about how these different types of hormones are related to breast cancer risk."
SOURCE: Cancer Epidemiology, Biomarkers, and Prevention, January 2008.
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