Taking hormone replacement therapy (HRT) after menopause is known to increase the risk of getting breast cancer, but women who take hormone therapy and then develop breast cancer have a lower risk of dying from the disease, a new study suggests.
Why?
"Hormone therapy seems to give you a particular type of cancer that is easier to treat," explained study author Sarah F. Marshall, a senior statistician at the University of California, Irvine. She reported her finding at the San Antonio Breast Cancer Symposium, in Texas.
The Study
Marshall and her colleagues evaluated nearly 2,800 postmenopausal women who were diagnosed with a primary invasive breast cancer after joining the study in 1995 and 1996. The researchers then tracked outcomes through the end of 2005, or until the women's death.
"We looked at self-reported use of hormone therapy before their diagnosis," Marshall said.
We compared three groups—those without [current or previous hormone use), those on estrogen alone, and those on estrogen-progestin."
Those taking estrogen-progestin had a 47% reduced risk of death from breast cancer during the follow-up compared to those with breast cancer who did not take hormone therapy. Those on estrogen alone had an 18% reduced risk of breast cancer death, but that was not statistically significant, she said.
We found that women who took hormone therapy before their diagnosis were more likely to be diagnosed with estrogen receptor-positive cancer, as well as having breast cancers that were more favorable in other ways, [such as being] smaller and detected at an earlier stage," Marshall said.
Estrogen-receptor positive breast cancers depend on estrogen to grow. Giving anti-estrogen therapy (such as tamoxifen) treats the cancer.
Implications
The study results may be somewhat reassuring for women who took hormone replacement therapy, Marshall said.
"The results of this study tell us that if you are taking HRT, your risk of getting breast cancer is higher, but your risk of dying from breast cancer is less than women with breast cancer who did not take hormones), said Victor G. Vogel, MD, MPH, the incoming national vice president of research for the American Cancer Society and a professor of medicine and epidemiology at the University of Pittsburgh.
Osteoporosis Drug Reduces Breast Cancer Risk
Estrogen protects bones but makes breasts more vulnerable to cancer. In a landmark study, women who took the osteoporosis drug raloxifene (Evista) were about half as likely to develop invasive, estrogen receptor (ER) positive breast cancer--the most common postmenopausal breast cancer-as women who did not take it. Raloxifene provides the protective effects of estrogen to bones while having antiestrogenic effects on breast tissue.
Downside: Like estrogen, the drug increases risk for blood clots and perhaps stroke.
Best: If you are considering medication for osteoporosis, ask your doctor if raloxifene is appropriate for you.
Drug that Blocks Tumor Growth
Trastuzumab (Herceptin) blocks a protein that promotes tumor growth. It is currently given primarily to early-stage patients whose tumors have a lot of the protein.
But: Two federally run studies suggest that some women who test negative for the protein actually may have enough of it to benefit from Herceptin.
