Panel: Mammogram benefits unclear. (Medical Groups Still Back Screening).

The benefits of screening mammography have once more been called into question, this time by an independent panel that reviewed the evidence on behalf of the National Cancer Institute.

The panel, called the Physician Data Query Screening and Prevention Editorial Board, concluded that while screening mammography may be beneficial, it's also possible that it's of no benefit for women at any age in reducing their chances of dying from breast cancer. The panel does not make practice recommendations.

"The evidence for the benefit of screening is weaker than we had previously" thought, and the primary impetus for this shift in thinking were the deep flaws pointed out in part by the Cochrane collaboration, said PDQ panel member Dr. Donald Berry, chair of the department of biostatistics at the University of Texas M.D. Anderson Cancer Center, Houston.

The Cochrane review of screening for breast cancer with mammography, published last fall, reexamined the conclusions of seven favorable randomized controlled trials and pointed out evaluation biases and design flaws that taken together cast doubt on the studies' findings of benefit.

In particular, the review focused on the best two trials of the group, the Malmo and the Canadian Trial, and found that they "failed to find an effect of screening on deaths ascribed to breast cancer after 13 years, according to Dr. Ole Olsen and Dr. Peter C. Cotzsche, who authored the collaborative report (Lancet 358[9290]:1340-42, 2001).

Furthermore, the Cochrane review estimated that screening increases the number of mastectomies by 20% and that in some cases mammography leads to unnecessary treatments because it identifies lesions that because of their slow growth or diffusiveness never would have become life threatening if left alone.

PDQ panel members said in interviews with this newspaper that ...