The study reviewed here found that 1 to 2 years after combination hormone replacement therapy (HRT) is stopped, breast cancer risk drops back to pre-HRT levels. Combination HRT has both estrogen and progesterone. These results were presented at the 2008 San Antonio Breast Cancer Symposium.
Researchers analyzed data from the large Women's Health Initiative (WHI), which has more than 15,000 participants. Earlier information from the WHI helped doctors understand the association between higher breast cancer risk and combination HRT used to manage menopausal side effects.
In this study, the researchers found that women who weren't taking combination HRT had a 65% to 95% lower breast cancer risk compared to women taking combination HRT. But 1 to 2 years after stopping HRT, women who had been taking HRT had the same breast risk as women who never took HRT.
The researchers also looked at data from another study that showed women who had taken HRT and were then diagnosed with breast cancer were more likely to survive breast cancer compared to women who never had taken HRT before diagnosis. The researchers aren't sure why HRT, which raises breast cancer risk, would make women who had taken it more likely to survive breast cancer.
Menopausal side effects can dramatically reduce some women's quality of life. These women have to weigh the benefits of HRT against the risks. If you're having severe hot flashes or other side effects from menopause and are considering taking HRT, talk to your doctor about how you can minimize your breast cancer risk. Be sure to discuss the pros and cons of different types of HRT and how you can take HRT for the shortest time possible. The research findings reviewed here suggest that once you stop taking HRT, your breast cancer risk will return to what it was before you started.
Keep these two points in mind when you talk to your doctor:
Together, you and your doctor can decide if HRT or another treatment might be right for you and your unique situation. If you do decide to use HRT, try to make healthy lifestyle choices that can lower your breast cancer risk. During and after HRT, make sure to follow the recommendations for breast cancer screening, including monthly breast self-exams, annual mammograms, and physical examinations by your doctor.
SAN ANTONIO, Dec. 16 (MedPage Today) -- The elevated breast cancer risk from hormone replacement therapy quickly dissipates after combined estrogen and progestin is discontinued, researchers reported here.
In the Women's Health Initiative -- the study that initially revealed the 24% or greater increased risk -- breast cancer occurrence dropped back to pre-hormone therapy levels within a year or two after women quit therapy en masse, said Rowan T. Chlebowski, M.D., Ph.D., of the University of California Los Angeles, and colleagues.
And another large study, reported here by Sarah Marshall of the University of California Irvine and colleagues, showed that women who developed breast cancer after having taken hormone replacement therapy were less likely to die from their cancer.
Overall, the findings from both studies, reported at the San Antonio Breast Cancer Symposium, were reassuring and unlikely to change guidelines from organizations such as the North American Menopause Society suggesting only short-term use of hormone replacement therapy, commented Peter Ravdin, M.D., Ph.D., of the University of Texas Health Science Center here. He moderated the session at which the findings were reported and was a co-author on the Women's Health Initiative study.
The hormone trial portion of the Women's Health Initiative included 16,608 postmenopausal women without prior hysterectomy randomized to placebo or combined hormone replacement therapy (0.625 mg of estrogen plus 2.5 mg progestin).
Prior analyses had shown that breast cancer incidence was similar between treatment groups in the first three years but then rose for a 24% higher risk at 5.2 years (HR 1.24, 95% CI 1.01 to 1.54).
When this risk, along with an increased risk of heart disease, was reported in 2002, prescriptions dropped nationally by about two-thirds over a period of only six months, Dr. Ravdin said. Women's Health Initiative patients were sent a letter and 96% discontinued therapy within the year.
Epidemiologic studies then documented a corresponding drop in breast cancer occurrence that started around the same time, but some challenged the association with hormone therapy replacement because changes in use of mammography couldn't be ruled out.
So, the researchers mapped trends in breast cancer risk and mammography during and after the hormone therapy intervention in the Women's Health Initiative.
They found that linear time varying hazard ratios for breast cancer with hormone therapy versus placebo rose fairly consistently in the years before the trial was stopped. Although afterward these fell with a steeper slope back to about the same baseline value, the hazard ratios were not significantly different (P=0.28 for trend), "perhaps because of the relative paucity of cases in the postintervention period."
The researchers repeated this measure, censoring women six months after they stopped hormone treatment.
In this sensitivity analysis, the post-intervention period saw an even sharper drop in risk for hormone-replacement group women (P=0.005 for a trend in difference).
Mammography rates were essentially identical between hormone and placebo groups in the years before and after hormone therapy was stopped in the trial, "so any changes in curves could not be attributed to mammography changes," Dr. Chlebowski said.
In the observational cohort of the study, the 25,328 women not using menopausal hormone therapy had a 65% to 79% lower risk of breast cancer compared with the 16,121 using combination hormone therapy before 2003.
But the difference in risk lost significance after most women quit hormone therapy. Hazard ratios for women who had been taking hormone replacement therapy dropped to 1.18 in 2003 (95% CI 0.84 to 1.67) and 1.20 in 2004 (95% CI 0.78 to 1.83).
Although women in this cohort who took hormone therapy were slightly more likely to get mammograms, the magnitude of the difference in rates between groups was consistent each year from 2001 through 2004.
Notably, women in the study diagnosed with incident breast cancer had similar overall survival whether they had taken hormones or not (HR 0.98, 95% CI 0.63 to 1.53).
However, Marshall's group noted quite a different effect on breast cancer survival in their analysis of the California Teachers Study.
In this observational cohort of 133,479 teachers and school administrators, 79% reported ever having taken hormone replacement therapy. The majority of these were on combined estrogen and progestin at baseline (41%), followed by current estrogen use alone (28%), and past hormone use (11%).
Among the 2,783 postmenopausal women who developed incident invasive breast cancer, breast cancer mortality was significantly lower among women who had ever used hormone therapy (4% combined, 6% estrogen only, and 9% never users, P<0.0001 ever versus never).
After adjusting for factors related to general health, such as comorbidities, smoking history, body mass index, and race or ethnicity, the survival advantage for those who had ever used estrogen or estrogen plus progestin remained (relative risk 0.67, 95% CI 0.44 to 1.00, and 0.40, 95% CI 0.26 to 0.63, respectively).
Likewise, adjusting for tumor type and treatment factors did not eliminate the advantage for women who had ever used combined hormone therapy (RR 0.53, 95% CI 0.33 to 0.84).
But, Drs. Chlebowski and Ravdin expressed skepticism about these findings, noting that the Million Women Study actually found increased risk of mortality.
Dr. Chlebowski reported being on the speakers' bureau for AstraZeneca, Abraxis, and Novartis and being a consultant for AstraZeneca, Genentech, and Lilly. His co-authors reported no conflicts of interest.
Marshall and colleagues reported no conflicts of interest. Dr. Ravdin reported no conflicts of interest.
Primary source: San Antonio Breast Cancer Symposium Source reference: Marshall SF, et al "Hormone therapy use before diagnosis and breast cancer survival in the California Teachers Study" SABCS 2008; Abstract 65.Additional source: San Antonio Breast Cancer SymposiumSource reference: Chlebowski RT, et al "Breast cancer after stopping estrogen plus progestin in postmenopausal women in the Women's Health Initiative" SABCS 2008; Abstract 64.
Breastcancer.org 7 East Lancaster Avenue, 3rd Floor Ardmore, PA 19003
Learn more about our commitment to your privacy
© 2010 Breastcancer.org - All rights reserved.
Breastcancer.org is a non-profit organization dedicated to providing information and community to those touched by this disease. Learn more about our commitment to providing complete, accurate, and private breast cancer information.
