The controversial link between hormone replacement therapy and breast cancer has resurfaced, with health experts claiming that there is no solid evidence that HRT increases breast cancer risks.
Today, according to the Journal of Family Planning and Reproduction Health Care, despite the Million Women Study in the UK reiterating the link between HRT and cancer, the panel of health experts believe that it doesn’t establish HRT as the cause of breast cancer.
However, they added that they couldn’t rule our HRT potentially increasing the chances of breast cancer developing.
The Million Women Study first issued their concerns about the link between HRT and breast cancer in 2003, funded by Cancer Research UK, when they discovered that combined HRT ‘doubled the risk of breast cancer compared to women who didn’t take it’.
However, experts from around Europe have analysed the study and concluded: “HRT may or may not increase the risk of breast cancer, but the Million Women study did not establish that it does.”
The reasons behind this conclusion pointed towards design flaws in the study that could flaw their findings. For example, breast cancer tumours detected in the women taking part in the study within a few months would have already been present in the woman’s body before she enrolled in the study. They argue that the Million Women study did not take this into account.
They also added that by inviting women to take part in the study would in itself have increased the number already aware of breast lumps or pre-cancerous changes, leading to higher numbers of cancers being detected (detection bias).
The experts also claimed that part of the date from the study was missing. In the third report from the Million Women Study, follow-up data on HRT use was not available for 57% to 62% of the study participants.
Concluding the study as, “indeed unreliable”, the experts added, "If the evidence was unreliable, the only effect of its massive size would have been to confer spurious statistical authority to doubtful findings.”
However, not all medical experts agree with the expert’s conclusion.
“Many studies have shown that HRT increases the risk of breast cancer and this study does not change that,” explains Dr Susie Jennings from Breakthrough Breast Cancer.
“It does suggest the risks may, in some instances, have been slightly overstated. However, we know that the risk of breast cancer starts to decrease as soon as a woman stops taking HRT.
“Anyone who has concerns about HRT should speak with their doctor. We hope the Breakthrough Generations Study, which is following 110,000 UK women over 40 years, will provide further clarity on this issue."
The Million Women study also claimed to find a link between HRT and ovarian cancer in 2007.
They stated that taking HRT increases the risk of developing ovarian cancer. Several small studies have shown this, and in April 2007 the results of a big trial of almost a million women showed that taking any type of HRT slightly increases the risk. The longer HRT is taken, the more the risk increases. But when the HRT is stopped, the risk goes back down to normal over a few years.
“The Million Women study showed that over five years there is one extra case of ovarian cancer in every 2500 women who take HRT, so the risk is only slightly increased. But, HRT also increases the risk of dying of ovarian cancer.
"The study showed that over 5 years, for every 3,300 women who take HRT, one extra woman will die due to ovarian cancer when compared to a group of women who have never taken HRT. If you are worried about HRT and ovarian cancer, you should speak to your GP, who can discuss the risks and benefits in your individual situation,” it stated on the Cancer Research website.