Women who participate in regular breast mammography screening have a 60% lower risk of dying from breast cancer within 10 years of diagnosis compared to those who don’t participate, a novel study shows.
While some have attributed improvements in breast cancer prognosis to advances in adjuvant therapy and chemotherapy, international researchers say their findings provide robust evidence that women whose breast cancer is diagnosed because of regular mammograms respond much better to treatment due to early detection,.
Most studies of breast screening effectiveness have relied on meta‐analyses of intention‐to‐treat estimates from RCTs, but epidemiologists including Dr Kerri Beckmann of the University of South Australia, looked at the annual incidence of breast cancers that were fatal within 10 years and within 11 to 20 years from diagnosis.
Their study used data from 52,348 women aged 40-69 years in Sweden during 39 years of screening.
Published in Cancer, they found that the benefit for women who chose to participate in an organised breast cancer screening program was a 60% lower risk of dying from breast cancer within 10 years after diagnosis (relative risk, 0.40;) and a 47% lower risk of dying from breast cancer within 20 years after diagnosis (relative risk, 0.53) compared with the corresponding risks for nonparticipants.
The researchers said this method reduced the risk of lead‐time bias given the long duration of follow‐up and also eliminated the potential influence of length time bias.
Dr Beckmann and colleagues said there had been a lot of recent discussion about the possible harms of participating in mammography but less about the harms of not participating.
“Our findings show that women who choose not to participate in screening experience a significantly higher rate of advanced breast cancers, a greater need for more extensive surgery, a much higher risk of upper body impairments and more extensive radiotherapy and chemotherapy,” she said
“For each breast cancer death prevented by screening, a woman is spared the terminal stages of this disease and gains an extra 16.5 years. It is time we focused on combining diagnosis and therapy instead of viewing them as independent, or worse, competing interests.”
“Our results, from precise, individual‐based data covering six decades, should provide women and their physicians with reassurance that participating in regular, high‐quality mammography screening is the best way to reduce the risk of a premature death from breast cancer,” they concluded.
Meanwhile, new data from the BreastScreen Australia program show that screen-detected breast cancers are less likely to cause death than breast cancers diagnosed in never-screened women.
The figures released by the Australian Institute of Health and Welfare (AIHW) show that 55.3% of screen-detected breast cancers were small (≤15 mm) compared with 27.6% of never-screened breast cancers.
Of the 73,440 breast cancers diagnosed in women aged 50–69 in 2002–2012, 31,968 (44%) were detected through BreastScreen Australia and 20,245 (28%) were diagnosed in women who had never screened.
After correcting for lead-time bias and screening selection bias, breast cancers detected through BreastScreen Australia had a 54% to 63% lower risk of causing death than breast cancers diagnosed in women who had never screened through BreastScreen Australia.
“This indicates that it is beneficial for a breast cancer to be detected through screening mammography rather than due to the breast cancer being symptomatic. This may be due to breast cancers detected through BreastScreen Australia being at an earlier stage than breast cancers that have become symptomatic,” the report authors said.