A Canadian study started the latest bout about the value of annual mammography for preventing breast cancer mortality.
The study concluded that annual mammograms in women ages 40 to 59 does not reduce breast cancer mortality compared to physical examination or usual care when adjuvant therapy for breast cancer is freely available.
Researchers drew their conclusion from a follow-up of 15 screening centers across Canada from 1980 to 1985. Results from nearly 90,000 women randomized to 5 annual mammography screens or a control of no mammography followed by usual care were linked to registry data.
Results appeared online Feb. 11 at BMJ.
The overall hazard ratio (HR) for death from breast cancer diagnosed during the screening period associated with mammography was 1.05 (95% CI, 0.85 to 1.30). The findings for women aged 40-49 and 50-59 were almost identical.
Cumulative mortality from breast cancer was similar between women in the mammography arm and in the control arm (HR, 0.99; 95% CI, 0.88 to 1.12). After 15 years of follow-up a residual excess of 106 cancers was observed in the mammography arm, attributable to over-diagnosis.
Overall, 22% of screen detected invasive breast cancers were over-diagnosed, representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial.
Researchers wrote, “Early detection could be of greater benefit in communities where most cancers that present clinically are larger and a higher proportion are node positive. However, in technically advanced countries, our results support the views of some commentators that the rationale for screening by mammography should be urgently reassessed by policy makers. Nevertheless, education, early diagnosis, and excellent clinical care should continue to be provided to women to ensure that as many breast tumours as possible are diagnosed at or less than 2 cm.”
ACP members quickly reacted to the news, sharing headlines and opinions on Twitter.
ACP Member Joseph Ross, MD, tweeted: “Important to clarify, Canadian RCT casts doubt on using mammography for breast cancer screening, not diagnostic mammography”.
In a reply, ACP Fellow Cary Gross, MD, FACP, said, “Yes screening is the key issue - a gateway to the subsequent tests too”.
ACP Resident/Fellow Member Paul A. Bergl, MD, tweeted a picture of an NFL player decked out in breast cancer awareness garb and stated: “Mixed #mammogram messages: Huge campaigns for awareness, but do we screen for #breastcancer?”
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