New guidelines for breast cancer screening are intended 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, released Monday by the Canadian Preventive Care Task Force, encourage women ages 40 to 74 to discuss breast cancer with their doctors and make a shared decision about performing a mammogram based in part on breast cancer preferences. a woman.
The guidelines are published in the Canadian Medical Association.
Earlier guidelines from 2011 recommended that women aged 40 to 49 routinely perform mammograms while those aged 50-74 were advised to take the screening test every two to three years.
The new guidelines are "aimed at a position of power that places decision-making in the hands of women in terms of what it prioritizes," said Ainsley Moore, a physician at McMaster University in Hamilton.
"I think there was a lot of confusion in the past about how the recommendations were interpreted," she said.
Although mammography offers the benefit of slightly reducing the risk of death from breast cancer, the test can also result in significant damage, she noted.
False positives, which can cause unnecessary suffering to women, are common and can lead to additional testing and possibly invasive biopsy.
For example, the task force found that for every 1,000 women 40-49 years old screened over a seven-year period, there were 294 false positives resulting in 43 unnecessary biopsies; even in the 70-74 age group, there were 219 false positives and 30 biopsies per 1,000 screened women.
Moore said there is also a risk of overdiagnosis and overtraining, with potential complications of radiation, chemotherapy and surgery.
The latest medical evidence, on which the updated guidelines are based, suggests that there may be a narrow margin between benefit and harm, leading the task force to make "conditional" recommendations based on patient preferences. They include:
- Women 40-49: The task force recommends against screening, but if a woman wants a mammogram she should discuss with her health provider the potential harm and benefits related to her age group.
- Those in their 40s face a greater risk of damage caused by false positives, overdiagnosis, and overtraining compared to other age groups. But the benefit is less: only one death from breast cancer is avoided for every 1,700 women who do mammograms, compared with one death for every 645 women aged 70-74 who are screened.
- Women 50-74: The task force recommends that women in this age group get mammograms every two to three years. This advice is also conditional, as some women may choose not to be examined if they are concerned about the overdiagnosis and the associated harm.
- There is no screening recommendation for women aged 75 years or older, and the guidelines do not apply to high-risk women, such as those with a BRCA1 mutation of BRCA2.
Moore said overdiagnosis is a major concern related to the nature of cancers: some are slow-growing tumors, while others are more aggressive and progress at a faster rate.
"The point is that these slow, turtle-breeding cancers will be detected at screening, but they would not cause symptoms in a woman's life. They would not become palpable lumps … they certainly would not cause death, "she said.
"The challenge is that doctors can not tell when they are diagnosed which of these cancers will progress and which will not. So the tendency is to treat all of them … because the consequences of not treating can also be significant.
"And then those are the issues that women are facing. Those are the issues that doctors are facing. "
Dawn Stacey, senior scientist at the Ottawa Hospital Research Institute, welcomed the amended council for women. "I'm excited about this new guideline, because in fact they recognize the preferences of women.
"The guidelines so far have been directives, so they said that's what you should do," she said. "The new guidelines are saying that this is what we suggest, but we really need to discuss this with women from both age groups."
So if having a mammogram is important to a woman in her 40s, Stacey said, "then it's okay."