or decades now many women have been scrupulously probing their breasts for suspicious lumps every month, using a rigorous approach developed to ensure that all areas of the breast are inspected carefully. They have performed this 15-minute ritual at the behest of health authorities and in the not unreasonable belief that such diligent searches may detect cancers early, when they are most curable. But last week researchers announced that a large and lengthy study in Shanghai had found no evidence that breast self-examinations reduced deaths from breast cancer. That could speed the demise of a practice that has become widely entrenched because it seemed intuitively sensible, offered women a tool to combat a fearsome disease and fit in with popular movements to give patients more control over their own health and bodies.

Debate over the value of breast self-examination has simmered for years, and some medical groups have stopped recommending them or at least toned down their exhortations. Now the China study, led by researchers from the Fred Hutchinson Cancer Research Center in Seattle, has provided the most authoritative evidence yet that self-examinations have been oversold. The study followed some 266,000 women, of whom half were given intensive and repeated instruction in how to examine their own breasts while the other half were not. After 11 years there were 135 breast cancer deaths among those who examined their breasts regularly and 131 in the control group, making it clear that the procedure did not save lives. The self-examiners proved unable to detect cancers at an earlier stage than the control group, eliminating the presumed advantage of the monthly probing.

Just why the self-examinations proved so ineffective is uncertain. One possibility is that the procedure is simply not sensitive enough to detect tumors any sooner than they would make their presence known to any woman reasonably alert to changes in her body. Another is that the women, though well instructed, may not have practiced self-examination with sufficient diligence.

The new findings have clear policy implications for developing countries, which would be foolish to squander their scarce health resources on large-scale campaigns to teach breast self-examination. The same lesson may also apply to the United States and other developed countries, where mass campaigns aimed at the general population should probably be curtailed. Rigorous self-examination is difficult to learn to do well and hard to continue long-term, and it causes lots of anxiety and benign biopsies. The only remaining uncertainty is whether women who are highly motivated to learn and perform the examinations exactingly may benefit. That issue has yet to be studied.

The two other pillars of current screening practices are mammography, which is still endorsed by most major medical organizations but whose effectiveness has been challenged by some statisticians, and clinical breast examinations performed by doctors or nurses. Clinical examinations are believed to be more effective than self-examinations, though the evidence is not considered very strong. Despite the latest verdict against self-examination, virtually all experts agree that it is important for women to be aware of the normal texture and appearance of their breasts and alert to any changes. That can be achieved without going through a complex monthly routine that may cause more anxiety and false alarms than it is worth.