Breast cancer risk and HRT – what matters most?

Posted by Liz on Jan 26, 2009 in HRT | 3 comments

Data from the San Antonio Breast Cancer Symposium last month provided definitive evidence that HRT increases the risk of breast cancer by 26% in menopausal women.  However, does route of administration (e.g., patch, oral) or type of  HRT matter?

According to a study in the journal Breast Cancer Research and Treatment, route of administration does not matter. But the progestagen component does.

Data were extrapolated from 80,377 postmenopausal women living in France and participating in E3N (a study designed to investigate risk factors for cancer) between 1990 and 2002.  At the study’s start, the average age of participants was 53 years. HRT types included estrogen only and estrogen plus progesterone, dydrogesterone combinations or other types of progesterone.

Over the study period 2,354 cases of invasive breast cancer occurred. Compared with women who never used HRT, women using estrogen alone had a 1.29-fold increased risk of developing breast cancer. However, breast cancer risk varied significantly depending upon the type of progestagen:

• Risk was significantly lower with estrogen-progestagen HRTS containing progesterone or dehydrogesterone than with estrogen combinations involving other types (e.g., nomegestrol acetate, norethisterone acetate, medroxyprogesterone acetate)
• The aformentioned combinations Ii.e. estrogen plus progesterone or  dehydrogesterone)  were associated with no or only a slight increase in breast cancer risk (1 fold greater or 1.16 fold greater, respectively).
• The results remained the same when analysis was restricted women whose age at the start of menopause could be most accurately determined.

Although the effect of progestagen remains somewhat unclear, and factors such as experimental conditions, length of time taking them and dose can influence results, the researchers did conclude that some HRT combinations may be safer than others.

Researchers also emphasize that further study is needed, and that medical experts are still unsure how HRT combinations affect other disease risks, such as heart disease, stroke and colorectal cancer.

Meanwhile, if you are taking HRT, talk to your health practitioner and find out which progestagen you’re taking. Better safe than sorry, right?!