Mammography Program in Norway Tied to Drop in Deaths
About a third of the reduction in breast cancer deaths attributed to screening mammography itself
WEDNESDAY, Sept. 22 (HealthDay News) -- The availability of a breast cancer screening program in Norway is related to a reduced rate of breast cancer mortality, though only about a third of the reduction can be attributed to the screening mammography itself, according to a study in the Sept. 23 issue of the New England Journal of Medicine.
Mette Kalager, M.D., of the Cancer Registry of Norway in Oslo, and colleagues compared the incidence-based rates of death from breast cancer in four groups, including two groups of women who were living in counties with screening (screening group) or without screening (nonscreening group) between 1996 and 2005, and two historical-comparison groups that, from 1986 through 1995, reflected the current groups. The screening program in Norway was started in 1996 and expanded geographically for the next several years. It consisted of an offer of screening mammography every two years for women between ages 50 and 69.
Among 40,075 women with breast cancer, the investigators found that the rate of death declined by 7.2 deaths per 100,000 person-years in the screening group compared to the historical screening group, and by 4.8 deaths per 100,000 person-years in the nonscreening group compared to the historical nonscreening group. A relative reduction in mortality of 10 percent was found in the screening group (P = 0.13). The researchers estimated that the difference in the reduction in deaths between the current and historical groups due to screening alone was 2.4 deaths per 100,000 person-years.
"Kalager et al help confirm that the decision about whether to undergo screening mammography is, in fact, a close call. Many observers will argue that because it is a delicate decision -- involving trade-offs among noncomparable outcomes -- it must be left to informed individuals to decide," writes the author of an accompanying editorial.