Jan. 11--The goal of cancer screening is to reduce the number of cancer deaths by finding tumors when they are still small and, presumably, easier to treat.
But a new study finds that in the case of breast cancer, improvements in treatment have barely changed the benefit of using mammograms as a screening tool.
The study, published Monday in Annals of Internal Medicine, explains that the value of early detection depends in part on the effectiveness of treatment. To understand the nature of that link, the team from the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle created a series of virtual clinical trials.
Each of these trials examined a hypothetical group of 100,000 American women, all age 50. About half of them were randomly assigned to get mammograms to check for signs of breast cancer, and the rest were not.
Some of these virtual trials were imagined to occur in 1975, shortly before mammograms were routinely used to screen for breast cancer; some took place in 1999, after combination chemotherapy and hormone therapy came on the scene; and some took place in 2015, to reflect the latest medical knowledge and treatments. Each trial used cancer prevalence and survival statistics from its era.
In the first round of trials, the researchers assumed that screening mammograms would reduce the incidence of advanced breast cancer by 15%. That was the median benefit seen among eight real-life clinical trials.
After building computer models to run these virtual clinical trials, the researchers compared the risk of dying of breast cancer for women who got mammograms and women who didn't.
