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JAMA Intern Med. Published online August 28, 2023.

A Meta-Analysis of Randomized Clinical Trials

Michael Bretthauer, MD, PhD1; Paulina Wieszczy, MSc, PhD1,2; Magnus Løberg, MD, PhD1; et al Michal F. Kaminski, MD, PhD1,2,3; Tarjei Fiskergård Werner, MSc4; Lise M. Helsingen, MD, PhD1; Yuichi Mori, MD, PhD1,5; Øyvind Holme, MD, PhD1; Hans-Olov Adami, MD, PhD1,6,7; Mette Kalager, MD, PhD1

Author Affiliations

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Key Points

Question: Cancer screening tests are promoted to save lives, but how much is life extended due to commonly used cancer screening tests?

Findings: In this systematic review and meta-analysis of 18 long-term randomized clinical trials involving 2.1 million individuals, colorectal cancer screening with sigmoidoscopy prolonged lifetime by 110 days, while fecal testing and mammography screening did not prolong life. An extension of 37 days was noted for prostate cancer screening with prostate-specific antigen testing and 107 days with lung cancer screening using computed tomography, but estimates are uncertain.

Meaning: The findings of this meta-analysis suggest that colorectal cancer screening with sigmoidoscopy may extend life by approximately 3 months; lifetime gain for other screening tests appears to be unlikely or uncertain.


Importance: Cancer screening tests are promoted to save life by increasing longevity, but it is unknown whether people will live longer with commonly used cancer screening tests.

Objective: To estimate lifetime gained with cancer screening.

Data Sources: A systematic review and meta-analysis was conducted of randomized clinical trials with more than 9 years of follow-up reporting all-cause mortality and estimated lifetime gained for 6 commonly used cancer screening tests, comparing screening with no screening. The analysis included the general population. MEDLINE and the Cochrane library databases were searched, and the last search was performed October 12, 2022.

Study Selection: Mammography screening for breast cancer; colonoscopy, sigmoidoscopy, or fecal occult blood testing (FOBT) for colorectal cancer; computed tomography screening for lung cancer in smokers and former smokers; or prostate-specific antigen testing for prostate cancer.

Data Extraction and Synthesis: Searches and selection criteria followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guideline. Data were independently extracted by a single observer, and pooled analysis of clinical trials was used for analyses.

Main Outcomes and Measures: Life-years gained by screening was calculated as the difference in observed lifetime in the screening vs the no screening groups and computed absolute lifetime gained in days with 95% CIs for each screening test from meta-analyses or single randomized clinical trials.

Results: In total, 2 111 958 individuals enrolled in randomized clinical trials comparing screening with no screening using 6 different tests were eligible. Median follow-up was 10 years for computed tomography, prostate-specific antigen testing, and colonoscopy; 13 years for mammography; and 15 years for sigmoidoscopy and FOBT. The only screening test with a significant lifetime gain was sigmoidoscopy (110 days; 95% CI, 0-274 days). There was no significant difference following mammography (0 days: 95% CI, −190 to 237 days), prostate cancer screening (37 days; 95% CI, −37 to 73 days), colonoscopy (37 days; 95% CI, −146 to 146 days), FOBT screening every year or every other year (0 days; 95% CI, −70.7 to 70.7 days), and lung cancer screening (107 days; 95% CI, −286 days to 430 days).

Conclusions and Relevance: The findings of this meta-analysis suggest that current evidence does not substantiate the claim that common cancer screening tests save lives by extending lifetime, except possibly for colorectal cancer screening with sigmoidoscopy.

I’m curious how comparing a handful of screening programs to all-cause mortality is approved? The ONLY comparison should be screening programs vs death due to THAT disease. So, a person either had a screen or they didn’t, and they died from that disease, or they didn’t. PERIOD. Every time I see a publication like this, I think wow, someone is getting paid to create a specific “study” for a specified outcome.