Researchers from University of Rochester Medical Centre have revealed that the risk of developing breast cancer due to taking hormone replacement therapy remains the same, regardless of the family history of disease.
"Although we know that family history is a risk factor, we don't know yet what it is about family history that conveys the risk," said Dr Robert E. Gramling, assistant professor of Family Medicine and of Community and Preventive Medicine at URMC.
"Some have proposed that it might be an increased sensitivity to estrogen, but our data did not support that notion. In fact, this study suggests the causal pathway based on family history is probably not estrogen sensitivity," he added.
During the study, the researchers analyzed data from the Women's Health Initiative randomized trial involving 16,608 postmenopausal women, between 50 and 79, who took hormone replacement therapy (HRT).
Of 16,608, 349 went onto develop invasive breast cancer. Gramling later studied direct interaction between the contributions that the two risk factors (HRT and family history) had on breast cancer risk.
The researchers found only a negligible degree of interaction, suggesting that HRT conveys no greater breast cancer risk to women with family history of breast cancer.
"The decision to use hormonal therapy, even for a short period of time, is very difficult for many women," Gramling said.
"We hope our data will provide postmenopausal women and their physicians more evidence to consider when weighing the risks versus benefits," he added.
The study is published online in the journal Epidemiology.