Another major contribution to the screening controversy came in 1995 with the publication of a review of eight clinical trials of breast cancer screening with mammography, published in the Journal of the Medical Association. The analysis found no evidence of a mortality reduction in women ages 40 to 49 with screening mammography.
Another analysis, also published in 1995 but in the journal Cancer, showed a statistically significant 24 percent reduction in breast cancer mortality in the 40-to-49 age group when data from the Canadian study were excluded. Inclusion of the Canadian data resulted in a nonsignificant mortality reduction.
Seeking to clear up uncertainty about the benefits of breast cancer screening in younger women, NCI held a consensus conference in early 1997. Many of the key players in the controversy from 1969 to the present participated in the conference, either as a panelist or speaker. Presentations and discussions focused only on the 40-to-49 age group.
Initially, the 13-member consensus panel reached a unanimous agreement about the conclusions and wording. After reading the draft consensus statement, two panelists disagreed with the document's language. When the panel could not reach a unanimous consensus, the final document included majority and minority opinions.
The majority opinion stated that "the data currently available do not warrant a universal recommendation for mammography for all women in their forties. Each woman should decide for herself whether to undergo mammography."
Authors of the minority report decided that the majority report placed that too much emphasis on the potential risks of mammography. The two panelists concluded that the data did support a recommendation for routine mammographic screening for all women ages 40 to 49.
The majority report touched off another round of public debate about the merits of mammography for younger women, including sometimes heated discussions at several professional meetings.
Subsequently, NCI issued a new statement on mammography, supporting screening every one or two years for all women ages 50 and older and screening every one or two years for average-risk women ages 40 to 49.
Still, the controversy would not go away. In 1997, data from another Swedish study published in the journal Cancer showed that mammographic screening of women ages 39 to 49 every 18 months reduced the mortality risk by 44 to 45 percent. An accompanying editorial included a reanalysis of the original Swedish study and showed a statistically significant mortality reduction in patients ages 40 to 49 when screened annually rather than biennially.
Another war of words ensued following publication in 2000 of statistical analyses by Scandinavian representatives of the Cochrane Collaborative. In short, two authors concluded in the journal Lancet that mammography does not save lives and exposes women to unnecessary surgical procedures.But a 2004 examination of the Scandinavians' methods showed that the authors reached their conclusions by excluding from analysis all positive studies, which they dismissed as being of poor quality.