Wednesday, 20 October 2010

HRT Cancer Scare - here we go again

Scare stories about HRT come round every few years. This time, according to the Daily Mail, HRT can now treble the chance of dying of breast cancer. Other shock headlines include 'Study shows HRT even riskier than thought'. The Washington Post goes with 'Hormones also raise death risk of cancer' and talks about 'powerful evidence'.

Menopause is still a taboo subject that a lot of women don't feel comfortable talking about, which makes it easier for myths and misunderstandings to spread.

If you read through to the end of some of the articles they do mention the stats but the headlines are what will stick in people's minds and may be the only part of the story they see - they are what's known as the take-away. A lot of people aren't that good at interpreting stats even if they get that far.

The headlines are based on research published in the Journal of the American Medical Association (JAMA). A study of 12,788 women for 11 years looked at women taking a combination of oestrogen and progesterone in a randomized placebo controlled trial.

Rowan Chlebowski of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center who led the analysis commented in the Washington Post that 'the risk in the study was low and barely met the threshold for being considered statistically significant' but he was 'confident that the risk was real'.

Barely Statistically Significant Cancer Risk! is not a headline you're likely to see. Even if such a headline existed, it's the C word that readers would remember. For cancer, there is no such thing as bad publicity.

The figures are these: in the placebo group there were 0.01% deaths and in the HRT group there were 0.03% deaths a year. That's 12 and 25 women in 12,000. The research also found that combination HRT was associated with more invasive breast cancers (0.42% of cases per year in the group as opposed to 0.34% in the placebo group).

With any apparently alarming statistics, it's the explanation of absolute and relative risk that rarely gets a look-in. If a disease kills two people in ten thousand one year and four people the next then the mortality rate has increased 100%. The chance of dying is still only four in ten thousand but that doesn't make for a good headline.

During the 2008 HRT breast cancer scare, also based on research by Rowan Chlebowski, Behind The Headlines pointed out something news stories glossed over: "In addition, the authors of the study point out that the differences seen should be interpreted with caution, as they may have resulted from differences in health seeking behaviours in the two groups of women after the trial. Women who had been told that they had been taking combined HRT at the end of the trial and knew of the cancer risk may have been more likely to seek medical attention for any suspicious symptoms than women who knew they had only received placebo.

BTH also pointed out that, despite predictable scare headlines: 'the study was not directly investigating any link between breast cancer and HRT. Instead it looked at whether HRT increased the chances of detecting an abnormality on a mammogram that then required a biopsy for further investigation; this would not necessarily involve a diagnosis of breast cancer.

'The main finding of the study was that the diagnostic accuracy of mammography was decreased in women who had taken combination HRT.

'This study only investigated one type and one dosage of combination HRT'.

There are many different types and levels of dosage. For example, the combination of estradiol and dydrogesterone (oestrogen/progesterone) sold as Femoston in the UK increases the risk for women in their 50s of having a stroke from 3 in 1000 to 4 in 1000. The risk of blood clots goes up from 3 in 1000 to 7 in 1000. And the risk of breast cancer goes up from 32 in 1000 by the age of 65 to 38 in 1000 if they take it for 5 years.

The risks of HRT are real in the sense that they do exist and the latest research seems to indicate that they are higher than previously believed. Risks also have to be offset against benefits - any good GP will explain this. Some of the risks can be considerably lessened by lifestyle changes and regular check-ups. There is a good basic introduction to HRT here.

Here's another risk: in 2004, the lifetime risk of dying in a motor vehicle accident was 1 in 82 in the US and 1 in 240 in the UK. Killer Cars!

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