Mammograms – X-ray screenings for lumps in breast tissue too tiny to be detected by self-examination – have been a staple of women’s health care for nearly 20 years. Although the recommended frequency and age guidelines have undergone several revisions, the premise that the earlier breast cancer is detected the better the prognosis for successful treatment is based upon good medical practice and just plain common sense.

A recent analysis, published in the British medical journal The Lancet, of the seven main clinical trials often cited to support the value of mammography seems to call that premise into question. Conducted by researchers at Denmark’s Nordic Cochrane Center in Copenhagen, the critique of those studies asserts that five, some conducted decades ago, were seriously flawed and finds that there is no scientific evidence that mammography reduces mortality from breast cancer or prolongs lives. Perhaps most startling is the conclusion that mammography actually results in an increase in mastectomies and radiation therapy, refuting the assumption that early detection allows for less drastic treatment.

The critique, endorsed with disturbing enthusiasm by The Lancet’s editor, is coming under criticism. The Danish researchers found bias in the way the five trials were conducted; other researchers find a higher degree of bias in the way the Danes evaluated those trials.

Health-conscious people are by more quite used to dueling studies – conflicts of interest, preconceived notions and simple contrariness are no more strangers to science than they are to any other field. The unfortunate result often is cynicism among the public; sometimes it even leads to hasty public policy decisions. Switzerland, for example, scrapped plans to institute a national mammography screening program, a decision health officials there say was heavily influenced by the Danish research. Critics, however, say the decision was driven by economic constraints during a recession and the research was merely a convenient excuse. In this country, women’s health experts already are worrying that the study may cause insurance companies to revisit their coverage of mammography.

At the core of this debate is the question of whether the period when a tumor can be detected by an X-ray but is too small to be felt in a physical examination is crucial to successful treatment. The debate has nothing to do with the effectiveness of breast cancer treatment itself – surgery, radiation, chemotherapy and hormone therapy have saved lives. But if the early detection mammography offers does not save more lives, the procedure offers no benefit and

is unnecessary.

The Danish research, however, proves no such thing. At best, it demonstrates once again the well-proven impossibility of conducting perfect scientific studies on human beings – the controlled circumstances of animal studies simply cannot be replicated. More studies are needed, as are more evaluations of existing studies. Until then, women over 40 should heed the advice of both the National Cancer Institute and the American Cancer Society and have annual mammograms. With no solid evidence to the contrary, the common sense about early detection still stands.