Value of screenings under scrutiny: Canadian study questions whether too many people are "over diagnosed".
Regular mammogram screenings do not reduce breast cancer death rates, a ground-breaking study of almost 90,000 women has found.
Experts say the findings add powerful new doubts to the value of screenings for women of any age and question whether too many people are ''over diagnosed'' by the popular test.
The Canadian study, published in the British Medical Journal, analysed women aged 40 to 59 over a quarter century and found that while screening made diagnosis of illness more likely, death rates from breast cancer were the same in women who had mammograms and those who had not.
"Women need to know there is no guaranteed benefit": Ian Olver, Cancer Council. Photo: Natalie Boog
And screening had harms - one out of five cancers found with mammography was over-diagnosed, meaning the lumps were not a threat to the woman's health and did not need chemotherapy, surgery or radiation.
Cancer Council Australia chief executive Ian Olver said while the findings are valuable, they would not lead to any immediate change in guidelines for mammography.
''There have been many studies that have shown advantages to getting screened,'' he said. ''But women need to know there is no guaranteed benefit. One study will never lead to a change in guidelines but we will continue to get experts to analyse it.''
He said women aged 50 to 74 were most likely to benefit from mammograms, and it was still recommended that this group be screened every two years.
Unnecessary diagnosis accounted for some breast tumours found by screening, Professor Olver said, but more importantly, BreastScreen Australia reports that biennial screening of women aged 50 to 69 can reduce death by one-third.
A professor in epidemiology at the University of Sydney, Alexandra Barratt, said the Canadian trial was one of a number of studies that had shown little benefit from mammography in reducing deaths.
''This study is not out of left field,'' Professor Barratt said. ''The concern is the level of over-detection of benign tumours.''
Many cancers, she said, grew slowly - or not at all - and did not require treatment. Some cancers even shrunk or disappeared on their own. But once cancer was detected, it was impossible to know if it was dangerous, so doctors treated them all.
''About 20 per cent of women who are screened are over diagnosed,'' Professor Barratt said.
With better treatments available, she said, including radiotherapy and endocrine therapy, there was a ''smaller window of opportunity'' for screening to be effective.
The study - one of the largest and most meticulous evaluations of mammography ever done - examined 89,835 women, with half of participants receiving annual screening over five years and those aged 50 to 59 having additional breast exams. The other half of women had no screening if they were aged 40 to 49 and only breast exams if they were aged over 50.
Over 25 years, 3250 women who had mammograms and 3133 who had no screening were diagnosed with cancer and 500 and 505, respectively, died of breast cancer.
In Australia, about 1.7 million women have at least one mammogram screening every two years.
It is recommended that well women without symptoms aged 50 to 69 attend the BreastScreen Australia for free two-yearly screenings.
Women aged 40 to 49 are eligible for screening but it is less effective because breast tissue in younger women is denser, making abnormalities harder to pick up.
Mammograms are not recommended for women under 40, but it is recommended all women check their breasts regularly so they can be aware of any changes to the way they feel.
''The information about mammography is constantly being updated and debated,'' Professor Barratt said. ''We should be helping women understand the potential benefits - and the possible harms.''
with the New York Times