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Hormone replacement therapy boosts breast cancer risk

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By David Liu, PHD

Sept 23, 2012 (foodconsumer.org) -- A new study in Breast Cancer Research suggests that using hormone replacement therapy (HRT) which is commonly used to relieve menopause symptoms like hot flashes and night sweats, can increase risk of breast cancer.

Early studies have already associated use of hormone replacement therapy with increased risk of breast cancer and heart disease.  But the current study led by Rudolf Kaaks of German Cancer Research Center (DKFZ) in Heidelberg, Germany and colleagues established the association between the hormone treatment with subtypes of breast cancer.

Based on the data from a European EPIC cohort, the researchers examined the effects of body mass index (BMI), waist and hip circumferences on the risk of estrogen-receptor negative (ER-) and progesterone-receptor negative (PR-) and ER-PR+ breast cancers within five-year age bands.  Among postmenopausal women, the combined effect of BMI and hormone replacement therapy was also examined.

BMI was not associated with risk of the ER-PR- breast cancer.  However, among postmenopausal women who never used hormone replacement therapy, BMI was correlated with breast cancer.  Those in the highest tertile of BMI were at 47 percent increased risk for breast cancer, compared to the lowest tertile.

Among women aged 49 years or younger, each 5 kg/m2 increase in BMI was associated with 21 percent reduced risk for ER+PR+ breast cancer whereas among those aged 65 or older, such an increase was correlated with 25 percent increased risk for the breast cancer.

After adjustment for BMI, waist and hip circumferences were not associated with risk of any  breast cancer subtype. This is understandable because waist and hip circumferences are associated with BMI and now that BMI was counted for its effect on the risk, waist and hip circumferences would no longer have a weight on the risk in the statistical analysis.

Compared to those who never used hormone replacement therapy, the current users were at a significantly increased risk of receptor negative and positive breast cancers, the increase was 30 percent and 74 percent respectively. The risk increase was weaker for ER-PR-breast cancer.

Hormone replacement therapy was more significantly associated with ER-PR- and ER+PR+ breast cancers among women with BMI of 22.5 kg/m2 or less, compared with overweight women with a BMI of 25.9 kg/m2 or higher.  The risk increase by the hormone treatment  was 74 and 133 percent, respectively.

The researchers concluded "An elevated BMI may be positively associated with risk of ER-PR- tumors among postmenopausal women who never used HRT. Furthermore, postmenopausal HRT users were at an increased risk of ER-PR- as well as ER+PR+ tumors, especially among leaner women. For hormone-receptor positive tumors, but not for hormone-receptor negative tumors, our study confirms an inverse association of risk with BMI among young women of premenopausal age. "

Breast cancer in many cases is preventable.  In the United States, one in eight women will eventually get diagnosed with breast cancer.    Each year in the U.S., an estimated 230,000 women are diagnosed with the disease, which kills about 40,000 annually, according to the National Cancer Institute.

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