earlier breast cancer screening reduces rates of later advanced cancers, research shows
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starting annual screening for breast cancer before the age of 50 results in a lower proportion of advance-stage breast cancer diagnoses, a new study from university of ottawa researchers has found.
the study, co-led by dr. jean seely, head of breast imaging at the ottawa hospital and professor at uottawa’s faculty of medicine, and dr. anna wilkinson, associate professor in the faculty of medicine at uottawa and a family medicine oncologist, was published in the most recent issue of current oncology.
wilkinson called it the first canadian study to demonstrate that screening policies for women between the ages of 40 and 49 impacted women between 50 and 59.
“women who are not screened in their 40s are presenting with late-stage breast cancer in their 50s,” she said.
the findings are relevant in ontario, where routine annual breast cancer screening, with prompts such as phone calls, begins at age 50. although women over 40 can be screened with referrals, that seldom happens, seely said. sometimes physicians will not refer patients because they are not aware they can get screened before age 50, she said. in other cases, patients don’t have or can’t get access to family physicians for referrals, something that has worsened since the covid-19 pandemic began.
seely said she and others were “actively asking” the ontario government to include women over 40 in the routine annual breast cancer screening program.
“it would save lives.”
when breast cancer is diagnosed at a later stage, women usually require more intensive treatment and have worse prognoses.
the research, using canadian cancer registry data housed at statistics canada, reviewed the data of 55,490 canadian women diagnosed with breast cancer between 2010 and 2017. among other things, they found that the provinces where screening began at age 40 had higher proportions of stage 1 breast cancer diagnoses and lower proportions of stages 2, 3 and 4 diagnoses compared to provinces and territories that did not begin routine screening with reminders.
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seely described it as a stage shift to more advanced cancers at diagnosis, meaning cancer was not being found earlier on, when it was less advanced.
“this has implications,” she said. “women’s lives were being lost in those provinces.”
she noted the five-year survival rate was 99 per cent when breast cancer was diagnosed at stage 1, and it decreased when cancer was diagnosed at more advanced stages. the five-year survival rate for breast cancer diagnosed at stage 4 was 25 per cent, she said.
in 2011, breast cancer screening guidelines in canada changed and no longer recommended annual screening begin at age 40.
seely and others have long argued that shift was based on research — the canadian national breast screening study — that was flawed. that study was long considered the gold standard and influenced breast screening guidelines in canada and around the world for decades.
she said a growing number of guidelines now call for screening at age 40. that includes recently updated usa national comprehensive cancer network guidelines that recommend annual screenings with mammograms for women with average risk begin at age 40.
seely has been among those warning that the pandemic is significantly adding to rates of advanced breast cancers being seen in ontario because of pauses and backlogs in breast screening.
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