A Canadian study that many experts say has major flaws has revived a debate about the value of mammograms.
The study suggests that these screening X-rays do not lower the risk of dying from breast cancer while finding many tumors that do not need treatment.
The study gives longer follow-up on nearly 90,000 women who were given either a breast exam by a nurse to check for lumps plus a mammogram or the breast exam alone.
After more than two decades of follow-up, death rates were similar in the two groups, suggesting little impact from mammograms.
Critics say the Canadians used outdated equipment and methods that made mammograms look unfairly ineffective. The study was published Wednesday in the British journal BMJ.