Estimated Lifetime Gained With Cancer Screening Tests: A Meta-Analysis of Randomized Clinical Trials

Abstract

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.

Figure 1.. Mechanisms for Benefits and Harms of Cancer Screening on Longevity of Life

The horizontal arrows illustrate 4 individuals who underwent screening. Arrows pointing right: 2 individuals who experienced screening benefit and live longer by early cancer detection and cure. Arrows pointing left: 2 individuals who experienced harm related to screening and died earlier than those without screening. The blue circle indicates population longevity effect of screening, which was calculated as all individual benefits minus all individual harms. ^aHarms of screening include perforation or bleeding during sigmoidoscopy and of diagnostics and treatment after screening, such as surgery, radiotherapy, and chemotherapy.

Figure 2.. Lifetime Gained With Commonly Used Cancer Screening Tests

The diamonds indicate point estimates of life days gained or lost for each screening test. Left and right arrows indicate 95% CIs. CT indicates computed tomography; FOBT, fecal occult blood testing; and PSA, prostate-specific antigen.