Trial reportJournal of medical screening2022
The randomized trial of mammography screening that was not-A cautionary tale.
Trial report in Journal of medical screening, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 13 papers, 1 of them a synthesis that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
13 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Screening for breast cancer: a systematic review update to inform the Canadian Task Force on Preventive Health Care guideline.Systematic reviews · 2024Pooled it
- Long-term effectiveness and overdiagnosis in the NHS breast screening programme: a cohort study with up to 33 years of follow-up.British journal of cancer · 2026Article
- A guide to cancer screening.Nature reviews. Clinical oncology · 2026Review
- Screening programmes and breast cancer mortality: an observational study of 194 countries.Bulletin of the World Health Organization · 2025Observational
- Breast Cancer Screening Interval: Effect on Rate of Late-Stage Disease at Diagnosis and Overall Survival.Journal of clinical oncology : official journal of the American Society of Clinical Oncology · 2024Article
- Another piece in the overdiagnosis jigsaw puzzle.BMJ oncology · 2023Article
- A plea for more careful scholarship in reviewing evidence: the case of mammographic screening.BJR open · 2023Review
- A population health assessment of screening mammography on breast cancer mortality in North Carolina.Breast cancer research and treatment · 2022Article
- The Impact of Organised Screening Programs on Breast Cancer Stage at Diagnosis for Canadian Women Aged 40-49 and 50-59.Current oncology (Toronto, Ont.) · 2022Article
- Misinformation and Facts about Breast Cancer Screening.Current oncology (Toronto, Ont.) · 2022Article
- Overdetection of Breast Cancer.Current oncology (Toronto, Ont.) · 2022Article
- How Did CNBSS Influence Guidelines for So Long and What Can That Teach Us?Current oncology (Toronto, Ont.) · 2022Article
- Marrying Story with Science: The Impact of Outdated and Inconsistent Breast Cancer Screening Practices in Canada.Current oncology (Toronto, Ont.) · 2022Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
5 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Two randomized trials were conducted in Canada in the 1980s to test the efficacy of breast cancer screening. Neither of the trials demonstrated benefit. Concerns were raised regarding serious errors in trial design and conduct. Here we describe the conditions that could allow subversion of randomization to occur and the inclusion of many symptomatic women in a screening trial. We examine anomalies in data where the balance would be expected between trial arms. "Open book" randomization and performance of clinical breast examination on all women before allocation to a trial arm allowed women with palpable findings to be mis-randomized into the mammography arm. Multiple indicators raising suspicion of subversion are present including a large excess in poor-prognosis cancers in the mammography trial arm at prevalence screen. Personnel described shifting of women from the control group into the mammography group. There is compelling evidence of subversion of randomization in Canadian National Breast Screening Study. Mis-randomization of even a few women with advanced breast cancer could markedly affect measured screening efficacy. The Canadian National Breast Screening Study trials should not influence breast screening policies.
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What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.