The new guidelines for screening breast cancer are designed to give women more voice in their health care decisions, taking into account their personal values and preferences rather than age and risk factor alone.
The guidelines published Monday by the Canadian Health Care Working Group encourage women aged 40 to 74 to discuss breast cancer screening with their doctors and make a joint decision whether to get mammography based on the woman's preferences.
The guidelines are published in the Canadian Medical Association.
The previous 2011 guidelines recommended that women aged 40-49 have routine mammograms, while those between the ages of 50 and 74 have been advised to receive a screening test every two to three years.
The new guidelines are "designed for an empowered position that puts decision-making in the hands of individual women in terms of what it gives priority," said Deputy Speaker of the Special Group, Einsley Moore, a family doctor at McMaster University in Hamilton.
"I think there was a lot of confusion in the past about how the recommendations were interpreted," she said.
While mammography offers the benefit of a small reduction in the risk of death from breast cancer, the test can also cause significant harm, she noted.
False positives that can cause unnecessary suffering are frequent and may lead to additional tests and, possibly, to an invasive biopsy.
For example, the Working Group found that for every 1 000 women aged between 40 and 49 who had passed a seven-year period, there were 294 false positive results, resulting in 43 unnecessary biopsies; even in the 70-74 age group, had 219 false positives and 30 biopsies per 1000 women.
Moore said there was a risk of both diagnosis and overvoltage, with potential complications from radiation, chemotherapy and surgery.
The latest medical evidence on which the updated guidelines are based suggests that there may be a narrow gap between benefits and damages, as head of the working group to make "conditional" recommendations based on patient preference. They include:
- Women 40-49: The specialist group recommends not screening, but if the woman wants mammography, she needs to discuss with her health provider the potential harm and benefits associated with her age group.
- Those in their 40s face a higher risk of damage from false positives, overdiagnosis and overload compared to other age groups. But the benefit is smaller: only one death from breast cancer is prevented for every 1,700 women who have mammograms, compared with one death for every 645 women aged 70 to 74 being tested.
- Women 50-74: The Task Force recommends that women in this age group receive mammograms every two to three years. This advice is also conditional, as some women may choose not to be reviewed if they are concerned about overdiagnosis and related harm.
- There is no recommendation for screening for women over 75 years of age and the guidelines do not apply to high-risk women such as those who carry BRCA1 genetic mutation of BRCA2.
Moore said that overdiagnosis is a major concern that relates to the nature of cancer: some are slowly growing tumors, while others are more aggressive and progress faster.
"The point is that these slow, turtle-growing cancers will be detected in screening, but they will not cause symptoms in the woman's life, they will not become noticeable lumps … they certainly will not cause death," she said.
"The challenge is that doctors can not tell at the time they are diagnosed which of these cancers will progress and which is not, so the tendency is to treat them all … because the consequences of not being treated , can also be significant.
"So, these are the problems women face, these are the problems faced by doctors."
Down Stacy, senior scientist at the Institute for the Study of Hospitals in Ottawa, welcomes the changed advice to women. "I am excited about this new direction because they are already recognizing women's preferences.
"The guidelines have so far been directives, so they said that's what you need to do," she said. "Exiting the new guidelines says that this is what we would suggest, but we really need to discuss this with women in both age groups."
So if mammography is important for a woman in her 40s, Stacy said, "then that's fine."