Women who get regular mammograms could reduce their risk of dying from breast cancer by 28 per cent, new research indicates.
The study is the largest and most rigorous yet to investigate the survival benefits of routine breast X-rays. Done by scientists from Sweden, Britain, Taiwan and the U.S., the research was based on 210,000 women aged 20 to 69 in Sweden.
Breast cancer deaths in North America and Europe have fallen by nearly 30 per cent since 1990. Experts are not sure how much of this is due to catching the disease early with mammograms.
“While mammography is largely accepted by the scientific and medical community as a benefit to women, there are still some who express doubts as to its value. This study goes a long way toward silencing the dissenting voices,” said the study’s leader, Stephen Duffy, professor of epidemiology at the Wolfson Institute of Preventive Medicine in London.
Other experts, though, said the study, printed this week in the medical paper Lancet, doesn’t prove the drop in deaths is due to early detection from X-rays rather than to advances in treatment.
Recommendations that women have regular mammograms have been based on seven landmark experiments done in the 1970s and 1980s that concluded the X-rays can cut deaths from breast cancer significantly.
However, confidence in breast screening was shaken by Danish scientists in 2000 who reanalyzed the experiments and concluded five were so flawed it was impossible to tell if routine mammograms saved lives. Several expert panels also concluded the studies were flawed, but not so dramatically that they dismissed their conclusions supporting mammograms.
In the latest study, researchers compared deaths from breast cancer diagnosed in the 20 years before mammogram screening was introduced with those diagnosed in the 20 years afterward. The X-rays were introduced in 1977 and offered to all women over 40.
During that time, 8,551 women developed breast cancer and 2,143 of them died from the disease.
The study found that, among women who got regular mammograms, the risk of dying from breast cancer was reduced by 44 percent compared to the early 1970s, when mammograms were not routinely done.
Mammograms can detect small tumors up to two years earlier than breast exams, providing more options for treatment.
However, they miss some cancer. They also too often flag benign lumps, causing anxiety, additional testing and biopsies.
However, women who refused mammograms still had a 16 percent drop in the chance of dying from the disease. That means their improved survival must have been the result of factors other than mammography, such as better drugs.