On 2014 Mar 23, Hilda Bastian commented:

Readers of this Cochrane review (Gøtzsche PC, 2013) may also be interested in other key reviews that assess much the same body of evidence. One of these is the systematic review undertaken for the US Preventive Services Taskforce (USPSTF) (Nelson HD, 2009). Another is the review by the Independent UK Panel on Breast Cancer Screening (Independent UK Panel on Breast Cancer Screening., 2012; Marmot MG, 2013; full report). In addition, the Canadian Task Force on Preventive Care used the USPSTF review as the basis for its findings and recommendations (Canadian Task Force on Preventive Health Care., 2011).

Update on 1 May 2014: Another review was published in JAMA in April 2014 (Pace LE, 2014). Its data on breast cancer death use the USPSTF review. The Swiss Medical Board published a review in April 2014 too: its findings and recommendations are based on interpreting the Cochrane, USPSTF and Independent UK Panel data (Takiura K, 1973). And I posted a guide to understanding mammography evidence on my blog at Scientific American.

Update on 30 October 2014: The WHO published a review of systematic reviews of trials and observational studies, with a search date up to December 2012 (WHO, 2014). Their data interpretation is similar to that of the UK Independent Panel, and they recommend 2-yearly screening from 50 to 69 years of age, where there's a good screening program and informed decisions. Their estimates of harm are lower than those of some others, taking into account more recent practice.

Differences in the estimates and conclusions about the effect of breast screening with mammography on breast cancer mortality between these reviews are not due to different trials being assessed. The differences principally arise from differing judgments on the strengths and limitations of individual trials, and a focus on local screening practices (which vary in terms of women's ages and whether screening is every one, two or three years).

There were also some differences in methodologies for analyzing the data. The meta-analyses done by both the review for the USPSTF and the Independent UK Panel used random effects models, there being differences between the trials. The review for the USPSTF used a Bayesian analytic framework. The Cochrane review used a fixed effects model. A fixed effect model assumes that the effect would be consistent across trials.

The Independent UK Panel by Marmot et al re-analyzed the trial data included in the 2011 version of the Cochrane review (with the same trials and estimates as this version). The Panel derived a comparison of the estimates of various authors, including the reviews included here (Independent UK Panel on Breast Cancer Screening., 2012). In order to prevent one woman's death from breast cancer, the number of women who would need to be invited for screening was estimated as:

• Cochrane review: 2,000
• USPSTF, for women aged 50 to 59: 1,339 and for women aged 60 to 69: 377

• Independent UK Panel, for women aged 55 to 79: 235

  In order to prevent one woman's death from breast cancer, the number of women who would need to be screened was estimated as:

• Canadian Task Force, for women aged 50 to 69: 720

• Independent UK Panel, for women aged 55 to 79: 180

The Independent UK Panel estimated that about 20% of breast cancers detected by mammography screening may be over-diagnosis. They recommended screening only every 3 years to reduce the risk. The Cochrane review suggested this may be 30% or more.

Longer term follow-up on one of the trials included in these reviews has subsequently been published (Canadian National Breast Screening Study, Miller AB, 2014). That trial is one of the trials judged by reviewers to be of high quality, and has consistently found no significant reduction in deaths attributed to breast cancer. It is the trial with results least favorable to mammography included in these meta-analyses.

A further systematic review has looked at the question of non-breast cancer mortality in breast cancer screening trials (Erpeldinger S, 2013). Breast cancer trials were not designed to answer this question. These authors conclude that the trials show neither a decrease nor increase in non-breast cancer mortality associated with screening.

The review for the USPSTF identified two systematic reviews relevant to the question of psychological harm from breast screening with mammography (Brewer NT, 2007, Brett J, 2005). The reviewers concluded false-positives are associated with distress, but no consistent effect on anxiety and depression has been shown for screening with mammography. A more recent systematic review has also looked at the impact of false-positive mammogram results, coming to similar conclusions (Bond M, 2013).

Marmot pointed out that the members of the UK Independent Panel were chosen both for expertise and not having previously published on the subject, to minimize the risk of a biased approach to analyzing and interpreting evidence (Marmot MG, 2013). The USPSTF commissioned the independent Agency for Health Care Research and Quality (AHRQ) to conduct the review used for its decision-making (Nelson HD, 2009).

On 2014 Mar 23, Hilda Bastian commented:

Readers of this Cochrane review (Gøtzsche PC, 2013) may also be interested in other key reviews that assess much the same body of evidence. One of these is the systematic review undertaken for the US Preventive Services Taskforce (USPSTF) (Nelson HD, 2009). Another is the review by the Independent UK Panel on Breast Cancer Screening (Independent UK Panel on Breast Cancer Screening., 2012; Marmot MG, 2013; full report). In addition, the Canadian Task Force on Preventive Care used the USPSTF review as the basis for its findings and recommendations (Canadian Task Force on Preventive Health Care., 2011).

Update on 1 May 2014: Another review was published in JAMA in April 2014 (Pace LE, 2014). Its data on breast cancer death use the USPSTF review. The Swiss Medical Board published a review in April 2014 too: its findings and recommendations are based on interpreting the Cochrane, USPSTF and Independent UK Panel data (Takiura K, 1973). And I posted a guide to understanding mammography evidence on my blog at Scientific American.

Update on 30 October 2014: The WHO published a review of systematic reviews of trials and observational studies, with a search date up to December 2012 (WHO, 2014). Their data interpretation is similar to that of the UK Independent Panel, and they recommend 2-yearly screening from 50 to 69 years of age, where there's a good screening program and informed decisions. Their estimates of harm are lower than those of some others, taking into account more recent practice.

Differences in the estimates and conclusions about the effect of breast screening with mammography on breast cancer mortality between these reviews are not due to different trials being assessed. The differences principally arise from differing judgments on the strengths and limitations of individual trials, and a focus on local screening practices (which vary in terms of women's ages and whether screening is every one, two or three years).

There were also some differences in methodologies for analyzing the data. The meta-analyses done by both the review for the USPSTF and the Independent UK Panel used random effects models, there being differences between the trials. The review for the USPSTF used a Bayesian analytic framework. The Cochrane review used a fixed effects model. A fixed effect model assumes that the effect would be consistent across trials.

The Independent UK Panel by Marmot et al re-analyzed the trial data included in the 2011 version of the Cochrane review (with the same trials and estimates as this version). The Panel derived a comparison of the estimates of various authors, including the reviews included here (Independent UK Panel on Breast Cancer Screening., 2012). In order to prevent one woman's death from breast cancer, the number of women who would need to be invited for screening was estimated as:

• Cochrane review: 2,000
• USPSTF, for women aged 50 to 59: 1,339 and for women aged 60 to 69: 377

• Independent UK Panel, for women aged 55 to 79: 235

  In order to prevent one woman's death from breast cancer, the number of women who would need to be screened was estimated as:

• Canadian Task Force, for women aged 50 to 69: 720

• Independent UK Panel, for women aged 55 to 79: 180

The Independent UK Panel estimated that about 20% of breast cancers detected by mammography screening may be over-diagnosis. They recommended screening only every 3 years to reduce the risk. The Cochrane review suggested this may be 30% or more.

Longer term follow-up on one of the trials included in these reviews has subsequently been published (Canadian National Breast Screening Study, Miller AB, 2014). That trial is one of the trials judged by reviewers to be of high quality, and has consistently found no significant reduction in deaths attributed to breast cancer. It is the trial with results least favorable to mammography included in these meta-analyses.

A further systematic review has looked at the question of non-breast cancer mortality in breast cancer screening trials (Erpeldinger S, 2013). Breast cancer trials were not designed to answer this question. These authors conclude that the trials show neither a decrease nor increase in non-breast cancer mortality associated with screening.

The review for the USPSTF identified two systematic reviews relevant to the question of psychological harm from breast screening with mammography (Brewer NT, 2007, Brett J, 2005). The reviewers concluded false-positives are associated with distress, but no consistent effect on anxiety and depression has been shown for screening with mammography. A more recent systematic review has also looked at the impact of false-positive mammogram results, coming to similar conclusions (Bond M, 2013).

Marmot pointed out that the members of the UK Independent Panel were chosen both for expertise and not having previously published on the subject, to minimize the risk of a biased approach to analyzing and interpreting evidence (Marmot MG, 2013). The USPSTF commissioned the independent Agency for Health Care Research and Quality (AHRQ) to conduct the review used for its decision-making (Nelson HD, 2009).