This systematic review, stimulated by inconsistency in secondary evidence, reports the benefits and harms of breast cancer (BC) screening and their determinants according to systematic reviews. A systematic search, which identified 9,976 abstracts, led to the inclusion of 58 reviews. BC mortality reduction with screening mammography was 15-25% in trials and 28-56% in observational studies in all age groups, and the risk of stage III+ cancers was reduced for women older than 49 years. Overdiagnosis due to mammography was 1-60% in trials and 1-12% in studies with a low risk of bias, and cumulative false-positive rates were lower with biennial than annual screening (3-17% vs 0.01-41%). There is no consistency in the reviews' conclusions about the magnitude of BC mortality reduction among women younger than 50 years or older than 69 years, or determinants of benefits and harms of mammography, including the type of mammography (digital vs screen-film), the number of views, and the screening interval. Similarly, there was no solid evidence on determinants of benefits and harms or BC mortality reduction with screening by ultrasonography or clinical breast examination (sensitivity ranges, 54-84% and 47-69%, respectively), and strong evidence of unfavourable benefit-to-harm ratio with breast self-examination. The reviews' conclusions were not dependent on the quality of the reviews or publication date. Systematic reviews on mammography screening, mainly from high-income countries, systematically disagree on the interpretation of the benefit-to-harm ratio. Future reviews are unlikely to clarify the discrepancies unless new original studies are published. This article is protected by copyright. All rights reserved.
BACKGROUND: Debates about the benefits and harms of mammography continue despite the accumulation of evidence. We sought to quantify the disagreement across systematic reviews of mammography and determine whether author or design characteristics were associated with conclusions that were favourable to the use of mammography for routine breast cancer screening.
METHODS: We identified systematic reviews of mammography published between January 2000 and November 2015, and extracted information about the selection of evidence, age groups, the use of meta-analysis, and authors' professions and financial competing interest disclosures. Conclusions about specific age groups were graded as favourable if they stated that there were meaningful benefits, that benefits of mammography outweighed harms, or that harms were inconsequential. The main outcome measures were the proportions of favourable conclusions relative to review design and author characteristics.
RESULTS: From 59 conclusions identified in 50 reviews, 42% (25/59) were graded as favourable by two investigators. Among the conclusions produced by clinicians, 63% (12/19) were graded as favourable compared to 32% (13/40) from other authors. In the 50-69 age group where the largest proportion of systematic reviews were focused, conclusions drawn by authors without financial competing interests (odds ratio 0.06; 95% CI 0.07-0.56) and non-clinicians (odds ratio 0.11; 95% CI 0.01-0.84) were less likely to be graded as favourable. There was no trend in the proportion of favourable conclusions over the period, and we found no significant association between review design characteristics and favourable conclusions.
CONCLUSIONS: Differences in the conclusions of systematic reviews of the evidence for mammography have persisted for 15 years. We found no strong evidence that design characteristics were associated with greater support for the benefits of mammography in routine breast cancer screening. Instead, the results suggested that the specific expertise and competing interests of the authors influenced the conclusions of systematic reviews.
Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer in men and their second or third leading cause of cancer death. Prostate-specific antigen (PSA) testing for PC has been in common practice for more than 20 years.
OBJECTIVES:
A systematic review of the scientific literature was conducted to determine the effectiveness of PSA-based population screening programs for PC to inform policy decisions in a publicly funded health care system.
DATA SOURCES:
A systematic review of bibliographic databases was performed for systematic reviews or randomized controlled trials (RCT) of PSA-based population screening programs for PC.
REVIEW METHODS:
A broad search strategy was employed to identify studies reporting on key outcomes of PC mortality and all-cause mortality.
RESULTS:
The search identified 5 systematic reviews and 6 RCTs. None of the systematic reviews found a statistically significant reduction in relative risk (RR) of PC mortality or overall mortality with PSA-based screening. PC mortality reductions were found to vary by country, by screening program, and by age of men at study entry. The European Randomized Study of Screening for Prostate Cancer found a statistically significant reduction in RR in PC mortality at 11-year follow-up (0.79; 95% CI, 0.67-0.92), although the absolute risk reduction was small (1.0/10,000 person-years). However, the primary treatment for PCs differed significantly between countries and between trial arms. The American Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) found a statistically non-significant increase in RR for PC mortality with 13-year follow-up (1.09; 95% CI, 0.87-1.36). The degree of opportunistic screening in the control arm of the PLCO trial, however, was high. None of the RCTs found a reduction in all-cause mortality and all found a statistically significant increase in the detection of mainly low-risk, organ-confined PCs in the screening arm.
CONCLUSIONS:
There was no evidence of a PC mortality reduction in the American PLCO trial, which investigated a screening program in a setting where opportunistic screening was already common practice. Given that opportunistic PSA screening practices in Canada are similar, it is unlikely that the introduction of a formal PSA screening program would reduce PC mortality.
BACKGROUND: Several popular screening tests, such as mammography and prostate-specific antigen, have met with wide controversy and/or have lost their endorsement recently. We systematically evaluated evidence from randomized controlled trials (RCTs) as to whether screening decreases mortality from diseases where death is a common outcome.
METHODS: We searched three sources: United States Preventive Services Task Force (USPSTF), Cochrane Database of Systematic Reviews, and PubMed. We extracted recommendation status, category of evidence and RCT availability on mortality for screening tests for diseases on asymptomatic adults (excluding pregnant women and children) from USPSTF. We identified meta-analyses and individual RCTs on screening and mortality from Cochrane and PubMed.
RESULTS: We selected 19 diseases (39 tests) out of 50 diseases/disorders for which USPSTF provides screening evaluation. Screening is recommended for 6 diseases (12 tests) out of the 19. We assessed 9 non-overlapping meta-analyses and 48 individual trials for these 19 diseases. Among the results of the meta-analyses, reductions where the 95% confidence intervals (CIs) excluded the null occurred for four disease-specific mortality estimates (ultrasound for abdominal aortic aneurysm in men; mammography for breast cancer; fecal occult blood test and flexible sigmoidoscopy for colorectal cancer) and for none of the all-cause mortality estimates. Among individual RCTs, reductions in disease-specific and all-cause mortality where the 95% CIs excluded the null occurred in 30% and 11% of the estimates, respectively.
CONCLUSIONS: Among currently available screening tests for diseases where death is a common outcome, reductions in disease-specific mortality are uncommon and reductions in all-cause mortality are very rare or non-existent.
IMPORTANCE: Le cancer du sein est la deuxième cause de décès par cancer chez les femmes aux États-Unis. Le dépistage par mammographie peut être associée à la mortalité par cancer du sein réduit, mais peut aussi causer des dommages. Les directives recommandent décisions de dépistage individualisation, en particulier pour les jeunes femmes.
OBJECTIFS: Nous avons examiné les éléments de preuve sur le bénéfice de la mortalité et les dommages principaux de la mammographie de dépistage et ce qui est connu sur la façon de personnaliser les décisions de dépistage par mammographie, y compris la communication des risques et des avantages pour les patients.
Acquisition des données: Nous avons cherché dans MEDLINE, de 1960-2014 à décrire (1) avantages de la mammographie, (2) les inconvénients de la mammographie, et (3) l'individualisation des décisions de dépistage et de promouvoir la prise de décisions éclairées. Nous avons également cherché manuellement la liste des articles clés récupérées, commentaires sélectionnés, les méta-analyses et recommandations de bonnes pratiques de référence. Nous avons évalué le niveau de preuve en utilisant les directives de l'American Heart Association.
RÉSULTATS: Le dépistage par mammographie est associée à une réduction globale de 19% de la mortalité par cancer du sein (environ 15% pour les femmes dans leur 40s et 32% pour les femmes dans leur 60s). Pour un 40 - femme ou 50 ans de subir 10 ans de mammographies annuelles, le risque cumulatif d'un résultat faussement positif est d'environ 61%. Environ 19% des cancers diagnostiqués au cours de cette période de 10 ans ne serait pas devenu cliniquement apparente sans dépistage (surdiagnostic), mais il existe une incertitude sur cette estimation. Le bénéfice net du dépistage dépend grandement sur le risque de cancer du sein référence, qui devraient être incorporées dans les décisions de dépistage. aides à la décision ont le potentiel d'aider les patients à intégrer l'information sur les risques et les avantages avec leurs propres valeurs et priorités, même si elles ne sont pas encore largement disponibles pour une utilisation dans la pratique clinique.
CONCLUSIONS ET PERTINENCE: Pour maximiser les avantages de la mammographie de dépistage, les décisions doivent être individualisées en fonction des profils et des préférences de risque des patients. Les modèles de risque et aide à la décision sont des outils utiles, mais d'autres recherches sont nécessaires pour optimiser ces ainsi que de quantifier surdiagnostic. La recherche devrait également explorer d'autres stratégies de dépistage du cancer du sein.
BACKGROUND: The effectiveness of prostate-specific antigen (PSA) for population screening has presented controversial results in large trials and prior reviews. We investigated the effectiveness of PSA population screening in a systematic review.
METHODS: The study was conducted using existing systematic reviews. We searched Ovid MEDLINE, Embase, Cochrane library, and the major Korean databases. The quality of the systematic reviews was assessed by two reviewers independently using AMSTAR. Randomized controlled trials were assessed using the risk of bias tool in the Cochrane group. Meta-analyses were conducted using Review Manager. The level of evidence of each outcome was assessed using GRADE.
RESULTS: Prostate-cancer-specific mortality was not reduced based on similar prior reviews (relative risk [RR] 0.93; 95% confidence interval [CI], 0.81-1.07, P=0.31). The detection rate of stage 1 prostate cancer was not greater, with a RR of 1.67 (95% CI, 0.95-2.94) and high heterogeneity. The detection rate of all cancer stages in the screening group was high, with a RR of 1.45 (95% CI, 1.13-1.85). No difference in all-cause mortality was observed between the screening and control groups (RR, 0.99; 95% CI, 0.98-1.01, P=0.50). Prostate-cancer-specific mortality, all-cause mortality, and diagnosis of prostate cancer at stages 3-4 showed moderate levels of evidence.
CONCLUSIONS: Differently from prior studies, our review included updated Norrköping data and assessed the sole effect of PSA testing for prostate cancer screening. PSA screening alone did not increase early stage prostate cancer detection and did not lower mortality.
This systematic review, stimulated by inconsistency in secondary evidence, reports the benefits and harms of breast cancer (BC) screening and their determinants according to systematic reviews. A systematic search, which identified 9,976 abstracts, led to the inclusion of 58 reviews. BC mortality reduction with screening mammography was 15-25% in trials and 28-56% in observational studies in all age groups, and the risk of stage III+ cancers was reduced for women older than 49 years. Overdiagnosis due to mammography was 1-60% in trials and 1-12% in studies with a low risk of bias, and cumulative false-positive rates were lower with biennial than annual screening (3-17% vs 0.01-41%). There is no consistency in the reviews' conclusions about the magnitude of BC mortality reduction among women younger than 50 years or older than 69 years, or determinants of benefits and harms of mammography, including the type of mammography (digital vs screen-film), the number of views, and the screening interval. Similarly, there was no solid evidence on determinants of benefits and harms or BC mortality reduction with screening by ultrasonography or clinical breast examination (sensitivity ranges, 54-84% and 47-69%, respectively), and strong evidence of unfavourable benefit-to-harm ratio with breast self-examination. The reviews' conclusions were not dependent on the quality of the reviews or publication date. Systematic reviews on mammography screening, mainly from high-income countries, systematically disagree on the interpretation of the benefit-to-harm ratio. Future reviews are unlikely to clarify the discrepancies unless new original studies are published. This article is protected by copyright. All rights reserved.
