TABLE I.

Screening recommendations, by organization

Organization	Target age (years)	Screening interval (years)	Period (years)	Number needed		Relative risk reduction
				To screen	To invite
Canadian Task Force on Preventive Health Care13	50–74	2–3	11	NA	Age 40–49: 2108	0.82
					Age 50–69: 721
Canadian Association of Radiologists14	40–74+a	Age 40–49: 1	40+	NA	NA	NA
		Age 50–74+: 1–2
U.S. Preventive Services Task Force15	50–74	2	10	NA	Age 40–49: 3333	Age 39–49: 0.88
					Age 50–59: 1250	Age 50–59: 0.86
					Age 60–69: 476	Age 60–69: 0.67
					Age 70–74: 769	Age 70–74: 0.80
American Cancer Society10	45+b	Age 45–54: 1	15	Age 40–49: 753	1770	0.75 Invited to screening
		Age 55: 2		Age 50–59: 462	835	0.62 Attending screening
				Age 60–69: 355	835
American College of Radiology16	40c	1	40+	NA	NA	NA
American College of Obstetricians and Gynecologists17	40–75	1–2	40+	NA	NA	NA
U.S. National Comprehensive Cancer Network18	40d	1	40+	NA	NA	NA
Cochrane Systematic Review19	NA	NA	10	NA	2000	0.81
U.K. Independent Review5	50–70e	3	20	50–79: 180	NA	0.80

^aContinue as long as life expectancy is 7–10 years.

^bContinue as long as life expectancy is ≥10 years.

^cContinue until life expectancy is <5–7 years.

^dContinue until life expectancy is ≤10 years.

^eThe U.K. National Health Service is in the process of extending breast cancer screening to include mammography in women 47–73 years of age.

NA = not available.