Table 4. Randomized Controlled Trials of Mammography Among Women Aged 39-74

Studies of Mammography Alone

Study (reference) Ages Median followup (years) Number of breast cancer deaths/ total number of women
(Screened)
Number of breast cancer deaths/ total number of women
(Control)
Breast cancer death rate per 1,000 women
(Screened)
Breast cancer death rate per 1,000 women
(Control)
Relative risk for breast cancer death
(95% Confidence Interval)
Absolute risk reduction per 1,000 women Number needed to invitea
Stockholm23 40-64 13.8 82/39,139 50/20,978 2.10 2.38 0.91 (0.65-1.27) 0.288 3,468
Gothenburg23 39-59 12.8 62/20,724 113/29,200 2.99 3.87 0.76 (0.56-1.04) 0.878 1,139
Malmö23 45-70 17.1 161/21,088 198/21,195 7.63 9.35 0.82 (0.67-1.00) 1.712 584
Swedish Two-County Trial26 40-74 17 319/77,080 333/55,985 4.14 5.95 0.68 (0.59-0.80) 1.809 553

Studies of Mammography Plus CBE

Study (reference) Ages Median followup (years) Number of breast cancer deaths/ total number of women
(Screened)
Number of breast cancer deaths/ total number of women
(Control)
Breast cancer death rate per 1,000 women
(Screened)
Breast cancer death rate per 1,000 women
(Control)
Relative risk for breast cancer death
(95% Confidence Interval)
Absolute risk reduction per 1,000 women Number needed to invitea
CNBSS-122 40-49 13 105/25,214 108/25,216 4.16 4.28 0.97 (0.74-1.27) 0.12 -
CNBSS-220 50-59 13 107/19,711 105/19,694 5.43 5.33 1.02 (0.78-1.33) -0.097 -
HIP19 40-64 16 232/30,239 281/30,256 5.46 6.89 0.79 1.438 883
Edinburgh18 45-64 13 156/22,926 167/21,342 6.80 7.82 0.79 (0.60-1.02) 1.020 980

aNumber needed to invite for screening to prevent one death from breast cancer 13-20 years after randomization.

Note: CBE indicates clinical breast examination; CNBSS, Canadian National Breast Screening Study; HIP, Health Insurance Plan of Greater New York.


Return to Document