TUESDAY, June 28 (HealthDay News) -- Mammography screening reduces breast cancer deaths even more than most experts have long believed, according to a new, large-scale Swedish trial.
In a study with a follow-up of nearly three decades -- the longest ever -- the researchers found that the benefits of the screenings become clearer as the decades roll on.
In fact, most of the benefits occur more than 10 years after mammography begins, and the screenings prevent far more breast cancer deaths than other, shorter studies have found, the report indicated.
"The big news is that if one considers the long-term effects on breast cancer mortality, the absolute benefit of screening in terms of number of lives saved is considerably greater than previously thought," said lead author Stephen W. Duffy, professor of cancer screening at Queen Mary, University of London.
Experts have long debated the best age for mammography screening to begin and how often it should be done.
In the new study, Duffy and colleagues looked at more than 133,000 women ages 40 to 74, living in two Swedish counties.
Researchers assigned them either to a group invited to mammogram screening or a group receiving usual care. The screening phase lasted about seven years. Women aged 40 to 49 got invited to screening every two years; women 50 to 74 every 33 months. The follow-up lasted 29 years.
For every 1,000 to 1,500 mammograms, one breast cancer death was prevented, Duffy's team found.
Other analyses have found, for instance, that for every 2,500 women aged 40 to 49 invited to screening, one death was prevented.
The study, whose authors reported no conflicts of interest, is published in the June 28 online edition of the journal Radiology.
"I was surprised and reassured by how long-lasting the effect was, and how consistent over three decades," Duffy said.
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