Women were recruited between 1990 and 1997, when technologies and treatments were not as effective as they are today.
The study is an update, 23 years after the start of the project, and presents results similar to those of the last report at 15 years. In the Lancet Oncology journal, researchers said the benefits manifested themselves in the first 10 years of screening, when there were 83 deaths among women who started screening around age 40, versus 219 in the group that started later.
In the longer term, there was little difference in mortality between the two groups. However, lead researcher Professor Stephen Duffy said lives could be saved by lowering the age for screening.
“This is a very long-term follow-up to a study that confirms that screening women under 50 can save lives. The benefit is seen mainly in the first 10 years, but the reduction in mortality persists in the long term at around one life saved per 1,000 women screened, ”he said.
“We are now doing more extensive screening and with better equipment than in the 1990s when the bulk of the screening in this trial took place, so the benefits may be greater than what we saw in this trial. study.”
Others were more circumspect. “There is evidence that lives have been saved by the type of screening that was done, under the circumstances that existed when the women involved were in their 40s, which is now long enough,” said Kevin McConway, professor. emeritus in applied statistics at the Open University.
He said there was also statistical uncertainty around the number of lives saved. “During these first 10 years, out of 10,000 women invited for screening, on average 16 died from breast cancer, while out of 10,000 women in the control group who did not undergo screening, on average 21 were deceased.
“These numbers indicate that lives have been saved. But they also indicate that deaths from breast cancer were quite rare among women this age. Since breast cancer deaths in younger women are not common, estimates of breast cancer death rates are not very precise, despite the fact that the trial involved 160,000 women.
In a journal commentary, Anthony B Miller, of the Dalla Lana School of Public Health at the University of Toronto in Canada, said the trial had not ended the debate on when to start screening. The trial did not include a control group of undetected individuals, he said, and he was surprised that few women were misdiagnosed with breast cancer – a big concern that led to an increase warnings in leaflets distributed by the NHS Breast Cancer Screening Program.
“One could argue that mammography breast screening should not be undertaken at any age, but rather that women should be encouraged to practice breast awareness, with mammography being used as a diagnostic test,” he said. written.