Screening Mammography & Breast Cancer Mortality: Meta-Analysis of Quasi-Experimental Studies

Abstract

BackgroundThe magnitude of the benefit associated with screening has been debated. We present a meta-analysis of quasi-experimental studies on the effects of mammography screening.MethodsWe searched MEDLINE/PubMed and Embase for articles published through January 31, 2013. Studies were included if they reported: 1) a population-wide breast cancer screening program using mammography with 5+ years of data post-implementation; 2) a comparison group with equal access to therapies; and 3) breast cancer mortality. Studies excluded were: RCTs, case-control, or simulation studies. We defined quasi-experimental as studies that compared either geographical, historical or birth cohorts with a screening program to an equivalent cohort without a screening program. Meta-analyses were conducted in Stata using the metan command, random effects. Meta-analyses were conducted separately for ages screened: under 50, 50 to 69 and over 70 and weighted by population and person-years.ResultsAmong 4,903 published papers that were retrieved, 19 studies matched eligibility criteria. Birth cohort studies reported a significant benefit for women screened <age 50, but not for women screened ages 50–69. Significant reductions in breast cancer mortality were observed in historical comparisons. For geographical comparisons, there was a significant 20% reduction in mortality for women <age 50 and a significant 21–22% reduction for women ages 50–69. Studies that tested the interaction of geographical and historical comparisons produced a pooled, significant 13–17% reduction in incident breast cancer mortality for women ages 50–69, but the effects in most individual studies were non-significant. All studies of women ages 70+ were non-significant.ConclusionsMammography screening may have modest effects on cancer mortality between the ages of 50 and 69 and non-significant effects for women older than age 70. Results are consistent with meta-analyses of RCTs. Effects on total mortality could not be assessed because of the limited number of studies.

Mammography Adherence in African-American Women: Results of a Randomized Controlled Trial

“…Studies have shown that African American women with lower incomes are generally less likely to be screened [50]. Several factors may explain the moderating effect of income.…”

Societal costs and effects of implementing population-based mammography screening in Greenland

“…The cumulated risk was adjusted for time of diagnosis, since women diagnosed with breast cancer before age 50 can inherently not benefit from a screening invitation after age 50. The RRR in breast cancer mortality because of invitation to mammography screening was assumed to be 20% on the basis of the literature search [6,8–11]. The absolute number of lives saved during a 10-year screening and follow-up period were estimated using the total number of women aged 50–69 years in Greenland from 2013.…”

“…The cost effectiveness of a breast cancer screening programme is influenced also by contextual factors in the healthcare system, the healthcare costs, the chosen screening interval, the chosen age interval of the women invited and the breast cancer epidemiology [7]. The magnitude of the effect of breast cancer screening is still disputed [8–11]. A relative risk reduction (RRR) in breast cancer mortality of 20% in women invited to screening compared with non-invited control groups was found by a UK panel and Cochrane, both only including RCT-studies in their systematic review [6,9].…”

“…A relative risk reduction (RRR) in breast cancer mortality of 20% in women invited to screening compared with non-invited control groups was found by a UK panel and Cochrane, both only including RCT-studies in their systematic review [6,9]. Two systematic reviews over incidence based studies estimated a 25–26% RRR [10,11], while a review of quasi-experimental studies found an effect of 16–23%, depending on the type of study design [8]. Consequently, the expected screening effect on breast cancer mortality is attached with uncertainty.…”

Mammography, Martin Yaffe, and Me: Response and Appreciation

“…In contrast, observational or service screening trials, although they frequently observe significantly higher benefit rates in the screened arm, often stumble in controlling for leadtime and length biases, although it can be agreed that they remain more appropriate for monitoring and comparing the effects of various screening programs. No unilateral argument can be made for the superiority of either the rct or the observational protocol design over the other; they have substantively different roles to play 21,22 and different capacities for handling overdiagnosis.…”