Mammography doesn't necessarily save lives

Mammography screening does not save many women's lives, reports a new study. It just provides early diagnosis with no impact on mortality or it over diagnoses disease.

Using DevCan 6.5.0, which the National Cancer Institute uses in estimating 10-year risk of diagnosis and 20-year risk of death, researchers at Dartmouth College developed a method to calculate the probability that a woman with screen-detected breast cancer has had her life saved by screening.

They determined that a 50-year-old woman has an estimated risk for having screen-detected breast cancer in the next 10 years of 1,910 per 100,000. Her observed 20-year risk for breast cancer is 990 per 100,000. Assuming that mammography reduces her risk for breast cancer by 20%, the risk for death without screening would be 1,240 per 100,000, suggesting that 250 per 100,000 women are spared. Thus, the likelihood that a woman with screen-detected breast cancer avoids death from her disease because of the screening is 13%. If screening mammography reduces breast cancer mortality by 5%, then the death benefit is only 3%. Analyses of women of different ages all yielded probability estimates below 25%.

Welch HG, Frankel BA. Likelihood that a woman with screen-detected breast cancer has had her "life saved" by that screening. Arch Intern Med. October 24, 2011. (Epub ahead of print.)