Screening for breast cancer: A systematic review update to inform the Canadian Task Force on Preventive Health Care guideline
Bibliographic record
Abstract
Abstract Objective This systematic review update synthesized recent evidence on the benefits and harms of breast cancer screening in women aged ≥ 40 years and aims to inform the Canadian Task Force on Preventive Health Care’s (CTFPHC) guideline update. Methods We searched Ovid MEDLINE® ALL, Embase Classic+Embase, and Cochrane Central Register of Controlled Trials to update our searches to July 8, 2023. Search results for observational studies were limited to publication dates from 2014 to capture more relevant studies. Screening was performed independently and in duplicate by the review team. To expedite the screening process, machine learning was used to prioritize relevant references. Critical health outcomes, as outlined by the CTFPHC, included breast cancer and all-cause mortality, treatment-related morbidity, and overdiagnosis. Randomized controlled trials (RCTs), non/quasi RCTs, and observational studies were included. Data extraction and quality assessment were performed by one reviewer and verified by another. Risk of bias was assessed using the Cochrane Risk of Bias 2.0 tool for RCTs and the Joanna Brigg’s Institute (JBI) checklists for non-randomized and observational studies. When deemed appropriate, studies were pooled via random-effects models. The overall certainty of the evidence was assessed following GRADE guidance. Results Three new papers reporting on existing RCT trial data and 26 observational studies were included. No new RCTs were identified in this update. No study reported results by ethnicity, race, proportion of study population with dense breasts, or socioeconomic status. For breast cancer mortality, RCT data from the prior review reported a significant relative reduction in the risk of breast cancer mortality with screening mammography for a general population of 15% (RR 0.85 95% CI 0.78 to 0.93). In this review update, the breast cancer mortality relative risk reduction based on RCT data remained the same, and absolute effects by age decade over 10 years were 0.27 fewer deaths per 1,000 in those aged 40 to 49; 0.50 fewer deaths per 1,000 in those aged 50 to 59; 0.65 fewer deaths per 1,000 in those aged 60 to 69; and 0.92 fewer deaths per 1,000 in those aged 70 to 74. For observational data, the relative mortality risk reduction ranged from 29% to 62%. Absolute effects from breast cancer mortality over 10 years ranged from 0.79 to 0.94 fewer deaths per 1,000 in those aged 40 to 49; 1.45 to 1.72 fewer deaths per 1,000 in those aged 50 to 59; 1.89 to 2.24 fewer deaths per 1,000 in those aged 60 to 69; and 2.68 to 3.17 fewer deaths per 1,000 in those aged 70 to 74. For all-cause mortality, RCT data from the prior review reported a non-significant relative reduction in the risk of all-cause mortality of screening mammography for a general population of 1% (RR 0.99, 95% CI 0.98 to 1.00). In this review update, the absolute effects for all-cause mortality over 10 years by age decade were 0.13 fewer deaths per 1,000 in those aged 40 to 49; 0.31 fewer deaths per 1,000 in those aged 50 to 59; 0.71 fewer deaths per 1,000 in those aged 60 to 69; and 1.41 fewer deaths per 1,000 in those aged 70 to 74. No observational data were found for all-cause mortality. For overdiagnosis, this review update found the absolute effects for RCT data (range of follow-up between 9 and 15 years) to be 1.95 more invasive and in situ cancers per 1,000, or 1 more invasive cancer per 1,000, for those aged 40 to 49 and 1.93 more invasive and in situ cancers per 1,000, or 1.18 more invasive cancers per 1,000, for those aged 50 to 59. A sensitivity analysis removing high risk of bias studies found 1.57 more invasive and in situ cancers, or 0.49 more invasive cancers, per 1,000 for those aged 40 to 49 and 3.95 more invasive and in situ cancers per 1,000, or 2.81 more invasive cancers per 1,000, in those aged 50 to 59. For observational data, one report (follow-up for 13 years) found 0.34 more invasive and in situ cancers per 1,000 in those aged 50 to 69. Overall, the GRADE certainty of evidence was assessed as low or very low, suggesting that the evidence is very uncertain about the effect of screening for breast cancer on the outcomes evaluated in this review. Conclusions This systematic review update did not identify any new trials comparing breast cancer screening to no screening. Although 26 new observational studies were identified, the overall quality of evidence remains generally low or very low. Future research initiatives should prioritize studying screening in higher risk populations such as those from different ages, racial or ethnic groups, with dense breasts, or family history. Registration Protocol available on the Open Science Framework: https://osf.io/xngsu/
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.079 | 0.185 |
| Meta-epidemiology (narrow) | 0.003 | 0.003 |
| Meta-epidemiology (broad) | 0.012 | 0.016 |
| Bibliometrics | 0.027 | 0.023 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.006 | 0.007 |
| Open science | 0.007 | 0.005 |
| Research integrity | 0.005 | 0.005 |
| Insufficient payload (model declined to judge) | 0.008 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".