The incidence of late-stage breast cancer has decreased by 37 percent since mammography was introduced more than 30 years ago, according to new research out of the University of Michigan Comprehensive Cancer Center.
For the study, published in the journal Cancer, researchers looked at early- and late-stage breast cancer diagnoses from 1977 to 1979 and compared it to diagnoses between 2007 and 2009. Based on trends observed before 1977 and trends that have continued since, the researchers took into account an estimated 1.3 percent increase in incidences of breast cancer each year.
Looking at the 1970s data, the researchers then projected the incidence of early-stage and late-stage breast cancer in 2007 and 2009 and compared it to the actual rates. They found that late-stage breast cancer incidence decreased by 37 percent per the projected rate, while early-stage breast cancer incidence increased by a 48 percent rate.
"When you factor in this temporal trend, our analysis shows that there has been a shift from late-stage to early-stage breast cancer over the last 30 years," senior study author Mark Helvie, director of breast imaging at the U-M Comprehensive Cancer Center, said in an announcement. "Not only are we detecting more early-stage cancer, but we are decreasing the number of late-stage cases that tend to be more challenging to treat and more deadly."
Helvie added that while there has been an increase breast cancer incidences, overall, the drop in late-stage diagnoses is promising.
"The findings confirm what breast cancer experts have long known--that widespread mammography screening has positively impacted the lives of women nationwide," Barbara Monsees, M.D., chairwoman of the American College of Radiology Breast Imaging Commission, said in an statement expressing support for the research.
A review of literature published in April on the benefits and risks of mammography found that while screening mammograms may reduce breast cancer mortality, the benefits of mammography are less--and the potential harms greater--than had once been expected.
What's more, researchers writing in the British Medical Journal in February reported that the results from a quarter-century long study involving 90,000 women cast doubt on the value of the screening test for women of any age. Led by Anthony Miller of the University of Toronto, the researchers said that death rates from breast cancer were similar in women who underwent mammograms and those who didn't.