14 DAY TRIAL // A new study carried out by the University of California, San Francisco, noted that the current serious drop in breast cancer rates is directly tied to reduced hormone therapy.
UCSF researchers analyzed over two million mammogram screenings carried out on nearly 700,000 women in the US, and, for the first time, they found a direct connection between a reduction in hormone therapy and a decrease in invasive breast cancer and in ductal carcinoma in situ (DCIS).
Hormone therapy started being used in the 1980s and 1990s, and almost 6 million American women found that it relieved postmenopausal symptoms.
The problem was that the rate of breast cancer started to rise constantly, so when in the mid-2002, a landmark report of the Women’s Health Initiative proved that the risks of hormone therapy surpassed its benefits, the method fell into disgrace.
Millions of women then gave up the estrogen and progestin therapy completely, or decided to reduce hormones drastically.
The striking decrease noted by the researchers led them to believe that they also have uncovered indirect evidence that hormones promote breast tumor growth, since the decline occurred in the age groups that most widely adopted then abandoned hormone therapy.
For their study, UCSF scientists reviewed 2,071,814 screening mammography examinations performed between January 1997 and December 2008 on almost 700,000 women, aged 40 and 79 years, as part of routine regular screening mammography.
The pattern they found was very clear: women between 50 and 69 years old were the most devoted hormone therapy users and had the biggest reduction in invasive breast cancer once they stopped – from 40 cancers out of 10,000 mammograms in 2002, to 31 cancers in 2005 and 35 cases of cancer in 2006.
Also, the rates of DCIS also dropped dramatically, once the hormone therapy was stopped, and in women over 70 years old, there was a parallel drop in cancer rates.
Noticeably, the researchers found that for women who were 40 to 49 years old at the beginning of the study, and were less likely to have adopted a hormone therapy, breast cancer rates remained unchanged, over the ten-year period.
The same group of scientists along with other researchers, had already noticed declines in invasive cancer between 2002 and 2003, in women aged 50 to 69 years, and these new results confirm their observations.
The statistics give a strong evidence that stopping hormone therapy reduces breast cancer risks, according to the authors.
For at least the past ten years, long-term hormone therapy has been discouraged and women were advised to at least reduce the hormone dose and the length of the treatment.
There were many studies which suggested that a therapy combining progestin and estrogen increased the risk of breast cancer and other disease, but this new study actually says that hormones help promote breast tumor growth of preexisting, latent hormone-dependent cancers.
This increases not only the incidence of invasive cancers, but also the ductal carcinoma in situ (DCIS) risk.
Senior author Karla Kerlikowske, MD, explained that “the study supports the idea that by giving the hormones we were promoting tumor growths by giving the hormones.
“The incidence of breast cancer decreases if you take the hormones away,” and this has been proved by “the fact that we’re continuing to see a decrease in invasive cancer,” hopefully meaning “that the effects of stopping the hormones may be long-lasting.”
Kerlikowske is also a professor of medicine, epidemiology and biostatistics at the UCSF Helen Diller Family Comprehensive Cancer Center, and co-director of the Women Veteran’s Comprehensive Health Center at SFVAMC.
And as scientists keep investigating this link between hormones and cancer, Kerlikowske says that using hormone therapy on a short term basis is “probably OK, but long term, it is not OK.’’
This research was supported by the National Cancer Institute-funded Breast Cancer Surveillance Consortium co-operative agreement, and the study has been published online by the “Journal of Clinical Oncology.’’