Abstract
BackgroundThe sensitivity of a mammography program is normally evaluated by comparing the interval cancer rate to the expected breast cancer incidence without screening, i.e. the proportional interval cancer rate (PICR). The expected breast cancer incidence in absence of screening is, however, difficult to estimate when a program has been running for some time. As an alternative to the PICR we propose the interval cancer ratio . We validated this simple measure by comparing it with the traditionally used PICR.MethodWe undertook a systematic review and included studies: 1) covering a service screening program, 2) women aged 50-69 years, 3) observed data, 4) interval cancers, women screened, or interval cancer rate, screen detected cases, or screen detection rate, and 5) estimated breast cancer incidence rate of background population. This resulted in 5 papers describing 12 mammography screening programs.ResultsCovering initial screens only, the ICR varied from 0.10 to 0.28 while the PICR varied from 0.22 to 0.51. For subsequent screens only, the ICR varied from 0.22 to 0.37 and the PICR from 0.28 to 0.51. There was a strong positive correlation between the ICR and the PICR for initial screens (r = 0.81), but less so for subsequent screens (r = 0.65).ConclusionThis alternate measure seems to capture the burden of interval cancers just as well as the traditional PICR, without need for the increasingly difficult estimation of background incidence, making it a more accessible tool when evaluating mammography screening program performance.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-782) contains supplementary material, which is available to authorized users.
Highlights
IntroductionThe sensitivity of a mammography program is normally evaluated by comparing the interval cancer rate to the expected breast cancer incidence without screening, i.e. the proportional interval cancer rate (PICR)
The sensitivity of a mammography program is normally evaluated by comparing the interval cancer rate to the expected breast cancer incidence without screening, i.e. the proportional interval cancer rate (PICR).The expected breast cancer incidence in absence of screening is, difficult to estimate when a program has been running for some time.As an alternative to the PICR we propose the interval cancer ratioInterval cancer ratio (ICR) 1⁄4 interval interval cancers cancers þ screen detected cancers
There was a strong positive correlation between the ICR and the PICR for initial screens (r = 0.81), but less so for subsequent screens (r = 0.65). This alternate measure seems to capture the burden of interval cancers just as well as the traditional PICR, without need for the increasingly difficult estimation of background incidence, making it a more accessible tool when evaluating mammography screening program performance
Summary
The sensitivity of a mammography program is normally evaluated by comparing the interval cancer rate to the expected breast cancer incidence without screening, i.e. the proportional interval cancer rate (PICR). The expected breast cancer incidence in absence of screening is, difficult to estimate when a program has been running for some time.As an alternative to the PICR we propose the interval cancer ratio. A high sensitivity is needed for a mammography screening program to fulfil its purpose This means the program should not have too many interval cancers, i.e. cancers that appear clinically after a negative screening result and before the scheduled screen. The aim of this article is to propose and validate an alternative performance indicator for the burden of interval cancers in an organized mammography screening program. We aim to validate this proposed measure by comparing with the PICR from studies of service screening programs for women aged 50-69.
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