Women taking menopausal hormone therapy that combines estrogen and progestin may be at higher risk of developing breast cancer than women taking estrogen alone, a new study has suggested.
Menopausal hormone therapies are given to relieve symptoms in post-menopausal women.
Researchers at UCLA’s Jonsson Comprehensive Cancer Center found that women taking the combination hormone therapy who experienced new onset breast tenderness had a 33 percent greater subsequent risk of developing breast cancer than women who did not experience breast tenderness.
In contrast, among women taking estrogen alone, those who experienced new-onset breast tenderness did not have a higher subsequent risk of breast cancer.
“This study showed that developing new breast tenderness after the start of hormone therapy was associated with increased breast cancer risk only in women on the combination estrogen plus progestin therapy, not estrogen therapy alone,” said study first author Dr. Carolyn Crandall, a professor of general internal medicine and a scientist with UCLA’s Jonsson Comprehensive Cancer Center
“The consistent theme we’ve run across throughout these studies is that estrogen and progestin compared to estrogen alone have a more marked effect on breast tissue.
“One theory is that there may be more growth of breast tissue, making the breasts more dense, when women take the combination therapy,” Crandall added.
The study appeared in the Nov. 17, 2011 in the early online edition of the peer-reviewed journal Breast Cancer Research and Treatment.