Breast cancer is the most common type of cancer in women (aside from skin cancer). Overall, the average risk of a woman in the United States developing breast cancer sometime in her life is about 13%. This means 1 of every 8 women will develop breast cancer. Women with genetic mutations of BRCA 1/2 have a significantly higher chance of developing breast cancer, and these represent 4.5% of breast cancers. See more about BRCA mutations here. Therefore, all women should follow screening guidelines (see below) and be under the care of a physician or similar health care provider.
.
Age is an important factor for breast cancer (see figure) with only about 9% of cases before age 40. Breast cancer is much more common after menopause than before but this increased risk does not appear to be due to menopause per se. Breast cancer develops in both women on hormone replacement therapy (HRT) and those who are not. The question is does HRT increase the risk for breast cancer? The answer may be surprising, but also potentially confusing. We now have the benefit of answering this question with about 2 decades of followup.
.
Again, strong evidence indicates that estrogen- only HRT does NOT increase the risk for breast cancer and appears to actually lower the risk. Even among women with a strong genetic predisposition of ovarian and breast cancer based on positive BRCA genes, estrogen only hormone supplementation does not increase the risk for breast cancer following risk reduction bilateral oophorectomy. Researchers conclude that “.. use of estrogen after oophorectomy does not increase the risk of breast cancer among women with a BRCA1 mutation and should reassure BRCA1 mutation carriers considering preventive surgery that HRT is safe. The possible adverse effect of progesterone-containing HRT warrants further study.” See study here.
On the other hand, long term oral combined therapy (estrogen + plus a form of progesterone) seems to increase the slightly increase the risk of of breast cancer but with no change in mortality. This is one of the reasons why some of the data is conflicting and confusing. Why does adding progesterone increase the rate of breast cancer? It may be because estrogens increase glandular tissue, while progestogens cause mitosis (cell division) of breast tissue and cancer represents uncontrolled mitosis.
One of the problems with earlier studies is that they used higher doses of hormone taking orally, by skin patch, or even injections. Also older studies used synthetic and non-natural hormones like premarin, which is made from horse urine. This older data likely does not apply to bioidentical hormones, especially at lower doses using using hormonal cosmetic cream and the 'safer' estrogen, estriol.
.
Topical forms of hormonal support also appear to be safer than oral forms because the liver changes some of the derivates. Topical use also seems to be more natural because the process of making hormones usually begins at the skin with vitamin D. Topical use also permits 'weaker' and 'safer' estrogens, such as estriol. Having said this, there are no current studies on 'safer' topical estrogens and long term follow up would require decades to complete. However, overwhelming current evidence favors use of topical hormonal cosmetic creams with benefits both to your skin (outer glow), as well as your inner health.
.
Looking again at the increased risk of continuous combined estrogen and progesterone HRT for breast cancer, this risk is relatively small compared to other factors. To put it into perspective, exercising 2.5 hours a week has a more significant effect on reducing the risk of breast cancer, as does other lifestyle issues (alcohol ingestion, smoking, obesity). Other factors are also important. For example, low levels of vitamin D may be a risk factor. Still, any increased risk is not welcome, and all women- on hormone supplementation or not- should follow screening guidelines and try to reduce their risk.
Since estrogen-only HRT does not increase the risk for breast cancer, why not use estrogen only hormonal HRT for everyone? Actually, this is the recommended form of hormonal supplementation for women without a uterus (typically from surgery, or hysterectomy). However, for the majority of women with a uterus, the only reason not to use estrogen-only HRT is because unopposed estrogen increases the proliferation of the uterine lining (endometrium) which can lead to endometrial hyperplasia and ultimately to endometrial cancer. So, although estrogen only HRT seems to decrease the rate of breast cancer and reduce breast cancer mortality, it increases the risk of endometrial cancer! More confusion. On the other hand, endometrial cancer is easier to monitor and treat than breast cancer, and the vast majority of women will be symptomatic with bleeding (unlike breast cancer which is initially silent). We can also reduce the risk of endometrial carcinoma by staying fit (obesity is a significant risk factor). For all these reasons, the apparent real risk of endometrial cancer may be over stated and, in my opinion, clearly less of a threat than breast cancer. See a detailed discussion of endometrial carcinoma here.
Because of the risk of uterine cancer, most authorities recommend adding progesterone to to 'protect' the uterine lining from over proliferation. Progesterone can be used continuously with combination therapy or cyclical. One cyclical strategy is to take progesterone for 14 days during a 3 month cycle. Others suggest non continuous progesterone in the last part of a 1 month cycle, and so better reflecting the normal fluctuations in hormones similar to premenopausal women.Another strategy is to use a more localized progesterone to protect the uterine lining, like a progesterone IUD.
.
When considering the potential risks of HRT or hormonal supplementation, realize that women started on HRT early still have a 30% reduction in all -cause mortality with long term follow up. This important fact cannot be under emphasized because it includes all factors, including cancers. Watch a very useful podcast about this and other benefits of hormonal supplementation here.
Based on the enormity of these data, it would appear that women can restore many of the hormones they need —without encountering adverse effects. Having said this, we need to remind readers that there are still no long-term safety data on the safety of even weak exogenously administered estrogens like estriol. Based on the totality of evidence that exists to date, it would appear that the estriol confers many benefits, while definitive protective measures against breast and other cancers can easily be incorporated into a healthy lifestyle.
Screening guidelines by the American Cancer Society for all women considered average risk:
- Women ages 40 to 44 should have the choice to start annual breast cancer screening with mammograms (x-rays of the breast) if they wish to do so.
- Women age 45 to 54 should get mammograms every year.
- Women 55 and older should switch to mammograms every 2 years, or can continue yearly screening.
- Screening should continue as long as a woman is in good health and is expected to live 10 more years or longer.
Women at high risk of breast cancer (for example those with BRCA mutations) may also have annual contrast magnetic resonance imaging (MRI).