Researchers who conducted one of the world's largest studies of mammograms said yesterday there was no truth to reports, circulating at medical conferences and among oncologists, that the results concluded women under 50 were more likely to die of breast cancer after they receive the tests.
Data from the study have not yet been published, but preliminary results from the large Canadian study suggest that women between the ages of 40 and 49 do not benefit from routine mammograms.
"We have been telling people for two years that there is as yet no benefit observed for women in this age group," said Dr. Cornelia Baines, deputy director of the Canadian National Breast Screening Study.
"But there are devastating implications to the claim of excess mortality, and this is certainly nothing we have released for publication," she said.
The Canadian National Breast Screening Study, which involves 90,000 women, was started in 1980 with the purpose of evaluating the usefulness of screening mammograms in women between the ages of 40 and 60.
Previous studies had shown the effectiveness of an annual test in women over 50, but doctors were hoping the Canadian trial would help them advise women in their 40s.
The Canadian researchers concede that early results suggested that deaths from breast cancer might be somewhat higher in women 40 to 49 who had mammograms.
But they said these findings later proved false. They said that they had discussed these preliminary results in private scientific sessions but that the data were meant only for those who attended.
But others faulted the Canadians for discussing the early findings and challenged even the remaining finding that mammograms were not useful for women in their 40s.
Most breast cancer experts in the United States remain convinced that annual mammogram are advisable in this age group.
The Canadian research group "began leaking information several months ago," said Dr. William Wood, chairman of the department of surgery at Emory University Medical Center in Atlanta. But because no data have been published, "it's all been very frustrating," he said.