(CBS) When it comes to breast cancer screening, how often women should get a mammogram is a hot topic for debate. Medical guidelines differ on the age women should start getting screened.
But new research might swing the argument towards the idea that more screening saves more lives, according to the longest follow-up study of its kind.
"I was surprised and reassured by how long-lasting the effect was, and how consistent over three decades," Dr. Stephen W. Duffy, professor of cancer screening at Queen Mary, University of London, told HealthDay.
The study, known as the Swedish Two-County Trial, kicked off over three decades ago. It divided over 133,000 women aged 40-74 into two groups - one where the researchers invited them for mammogram screening every 24 to 33 months over a seven-year period, the other where they received "usual care" and didn't get screening invitations. What happened? At the end of study, there were 30 percent fewer breast cancer deaths in the screening group.
Cut to 29 years later, researchers wanted to see if regular mammogram screening had long-term effects on reducing breast cancer deaths. They found from the follow-up study - published in the June 28 issue of "Radiology" - that about 400 to 500 women needed to undergo screening every two to three years, over a seven-year period, to prevent one breast cancer death.
"Our results indicate that in 1,000 women screened for 10 years, three breast cancer deaths would be prevented," Duffy told Reuters. He said most of the prevented deaths would have occurred 10 years after screening started.
What does this mean?
"The long-term benefits of screening in terms of deaths prevented are more than double those often quoted for short-term follow-up," Duffy said in a written statement.
Medical guidelines differ on how often women should get a mammogram. The American Cancer Society says women should get one every year starting at age 40. The U.S. Preventive Services Task Force disagrees. It recommends against routine mammograms for women in their 40s, saying women in their 50s should get one every other year.
What should women do?
"Everyone must make up their own mind" Duffy told Reuters. "But certainly from combined results from all the screening trials, mammography in women aged 40-49 does reduce deaths from breast cancer."
The National Cancer Institute has more on breast cancer screening.