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HRT breast cancer risk varies by personal characteristics

By jeremyc | August 18, 2010

Source: MedWire News

Breast cancer risk increases with increasing duration of hormone replacement therapy (HRT), with continuous combined estrogen-progestin therapy (EPT) users at the greatest risk for developing the disease, researchers report.

Women need detailed information regarding the risks associated with HRT to optimize their own risk-benefit assessments, say Giske Ursin (University of Oslo, Norway) and colleagues.

In the present study, Ursin and team investigated breast cancer risk in relation to HRT use among 56,867 peri- and postmenopausal women participating in the California Teachers Study. The researchers were particularly interested in the formulation and duration of HRT use, and how other established breast cancer risk factors might modify the risk associated with the latter.

During a mean follow-up of 9.8 years, 2857 (5%) women were diagnosed with invasive breast cancer, and the researchers found that the risk for breast cancer increased with increasing duration of estrogen therapy (ET) and EPT use.

Women reporting 15 or more years of ET use at baseline use had a 19% increased risk for breast cancer, compared with women who had never used HRT. The risk was 83% higher among women using EPT for 15 years or more.

When the researchers assessed average monthly HRT use, they found that breast cancer risk was highest among women using EPT regimens continuously. These women had a 75% increased for breast cancer compared non-users, whereas short sequential users (10 days or fewer per month) had a 40% increased risk and long sequential users (between 10 and 28 days per month) had a 49% increased risk.

Breast cancer risk also seemed dependent on body mass index (BMI). Compared with non-users, the risks associated with 15 or more years EPT and ET use were approximately doubled for women with BMIs below 29.9 kg/m2, whereas women women with a BMI of 30 kg/m2 or above had no significantly increased breast cancer risk.

Of note, elevated risks associated with EPT and ET use were confined to tumors that were positive for both estrogen and progesterone receptors, and those that were human epidermal growth factor receptor (HER)2-positive. The risk was slightly diminished for HER2-negative tumors.

“These findings, taken in context of the larger literature on this topic, continue to underscore the need to personalize risk-benefit discussions for women contemplating the use of HRT,” conclude Ursin and co-authors in the journalCancer Epidemiology Biomarkers and Prevention.

Topics: | Breast cancer |

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