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 invite^a
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 invite^a
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.