Researchers from the Cochrane Collaboration, an international organisation that evaluates medical research, came to that conclusion after reviewing two previously published population-based studies involving 388,535 women.

In both trials conducted in Russia and China investigators randomly assigned women to one of two groups. One group was taught how to perform breast self-exams and was instructed to do them regularly; the control group was not.

Among the 587 participants who died of breast cancer during the course of the studies, 292 women had dutifully performed breast self-exams and 295 had not a minuscule difference that suggests there is no benefit from self-checks, the Time megazine reported.

But the authors go further, issuing a strong warning that breast self-exams may do unnecessary harm, because they put women at risk for unneeded treatment. In the two studies, women who performed breast self-exams underwent 3,406 biopsies with benign results, nearly twice as many as women in the control groups.

Peter Gotzsche, director of the Nordic Cochrane Centre in Denmark and a co-author of the review, says biopsies are often the first step on the path toward further testing and increasingly invasive diagnostic tests.

The report cites studies suggesting that women who travel that route often emerge with scars, breast deformities and emotional wounds.

A benchmark study from 1998, published in the Journal of Public Health Medicine, indicates that five months after a benign surgical biopsy, 61 per cent of women still struggled with symptoms of anxiety and psychological distress, including trouble sleeping, change in appetite and a general malaise fuelled by thoughts of breast cancer.

Yet Gotzsche and his co-author close their paper on a final ambiguous note: "It would be wrong, however, to conclude that women need not be aware of any breast changes." The question is, how does a woman become aware of any changes in her breasts without actually checking them?

"Common sense suggests that it is not possible for us to be 'breast aware' without examining [the breasts]," says Dr. Carolyn Runowicz, director of the Carole and Ray Neag Comprehensive Cancer Center at the University of Connecticut Health Center.

And, in fact, previous studies have shown that many women do find their own cancerous breast lumps. One such study, published in 2000 in the Medical Journal of Australia, shows that 35 per cent of breast-cancer patients happened upon their own lump. Advocates of breast self-exams see that study as a slam-dunk for their cause.

But a closer inspection of the data reveals that researchers did not ask how the women made their discoveries: did they use bona-fide breast self-exams or did they find the physical changes by chance?

Konrad Jamrozik, a professor of evidence-based health care at the University of Queensland in Australia and the study's lead author, shrugs off the question as irrelevant.