Breast screening a lifesaver, despite what the Canadians might say
Cancer experts have backed the life-saving benefits of the national breast screening program despite claims in a Canadian study that regular mammography was no better than physical examination in helping women survive breast cancer.
The Federal Health Department and Cancer Council Australia said the Canadian study, which over 25 years compared the cancer survival rates of women aged between 40 and 59 years who had annual mammograms compared with those who received physical examinations, was “not relevant” to Australia.
The study, published in the British Medical Journal, involved 89,000 40 to 59-year-old women without a history of breast cancer who were randomly assigned to one of two groups – the first of which received regular mammograms, and the second who only received physical examinations.
The researchers found that the breast cancer death rates were similar in both groups.
After 20 years, 3133 women in the physical exam control group had been diagnosed with breast cancer, while 3250 subjects from the mammography group had the diagnosis – 500 of whom died from breast cancer, compared with 505 women from the control group.
But Cancer Council Chief Executive Officer Professor Ian Olver said the weight of scientific evidence showed mammographic screening was an effective and lifesaving initiative.
Professor Olver said that while the Canadian study found no mortality benefit for women aged 40 to 59 years, the biggest benefit of breast screening was for women aged 50 years and older.
“So you are trying to compare apples with oranges if you try to apply conclusions from the Canadian study to Australia, where mammography is appropriately targeted through the BreastScreen Australia program,” he said.
Professor Olver said that, while the Canadian study looked at the results of screening over a five-year period, a more comprehensive review of BreastScreen outcomes conducted over 15 years showed a mortality benefit of between 21 and 30 per cent.
He added that the Canadian study was conducted in the 1980s, using technology and procedures that “have no relevance to contemporary Australia”.
“The message is simple: the weight of scientific evidence supports mammography as a population screening tool, and many Australian women are alive today thanks to 20 years of BreastScreen,” Professor Olver said.
In addition to its other conclusion, the Canadian study found that one in five cancers detected using mammography – and which were subsequently treated – posed no threat to health, and did not need treatment with conventional techniques, such as surgery, chemotherapy or radiation.
But the Health Department said this did not undermine the validity of population-based screening using mammography.
A Department spokeswoman said the majority of cancers identified through screening would be progressive and become symptomatic if left untreated.
The spokeswoman admitted it was likely that some cancers identified may never have progressed – what is sometimes referred to as over-diagnosis.
“[But], it is important to note that these are breast cancers, [and] at this time it is not possible to precisely predict at diagnosis which cancers would not progress,” she said, adding that a 2009 evaluation of BreastScreen found a 25 per cent reduction in breast cancer deaths among women aged between 50 and 69 years.