Early detection of breast cancer reduces rates of later advanced cancers, research shows

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Beginning annual breast cancer screening before age 50 results in a lower proportion of advanced-stage breast cancer diagnoses, a new study from researchers at the University of Ottawa has found.

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The study, co-led by Dr. Jean Seely, chief of breast imaging at Ottawa Hospital and professor at uOttawa School of Medicine, and Dr. Anna Wilkinson, associate professor at uOttawa School of Medicine and oncologist at family medicine, was published in the most recent issue of Current Oncology.

Wilkinson called it the first Canadian study to show that screening policies for women ages 40-49 affect women ages 50-59.

“Women who are not screened at age 40 develop late-stage breast cancer at age 50,” he said.

The findings are relevant to Ontario, where routine annual breast cancer screening, with prompts such as phone calls, begins at age 50. Although women over 40 can get tested with remissions, that rarely happens, Seely said. Sometimes doctors don’t refer patients because they don’t know they can get tested before age 50, she said. In other cases, patients do not have or cannot access family doctors for referrals, something that has worsened since the COVID-19 pandemic began.

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Seely said she and others were “actively asking” the Ontario government to include women over 40 in the annual routine breast cancer screening program.

“It would save lives.”

When breast cancer is diagnosed at a late stage, women often require more intensive treatment and have poorer prognoses.

The research, using data from the Canadian Cancer Registry housed at Statistics Canada, reviewed data on 55,490 Canadian women diagnosed with breast cancer between 2010 and 2017. Among other things, they found that provinces where screening began at age 40 years had higher proportions of stage 1 breast cancer diagnoses and lower proportions of stage 2, 3, and 4 diagnoses compared with provinces and territories that did not initiate routine reminder screening.

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Seely described it as a change in stage to more advanced cancers at the time of diagnosis, meaning the cancer was missed earlier, when it was less advanced.

“This has implications,” he said. “The lives of women were being lost in those provinces.”

He noted that the five-year survival rate was 99 percent when breast cancer was diagnosed at stage 1 and decreased when the cancer was diagnosed at more advanced stages. The five-year survival rate for breast cancer diagnosed at Stage 4 was 25 percent, she said.

In 2011, breast cancer screening guidelines in Canada changed and it is no longer recommended that annual screening begin at age 40.

Seely and others have long argued that the change was based on research, the Canadian National Breast Detection 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 require screening at age 40. That includes recently updated guidelines from the US National Comprehensive Cancer Network that recommend annual screening with mammography for average-risk women age 40 and older.

Seely has been among those warning that the pandemic is significantly increasing the rates of advanced breast cancers seen in Ontario due to pauses and delays in breast screening.