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.
Interesting study and frankly kind of depressing. Looks like we need to start looking for either better screening tests or more selective screening tests.
The huge problem with this review is the selective nature of the literature chosen, especially with respect to breast screening. Miller et al is viewed as problematic by many suggesting that breast cancer mortality is higher in the screened arm in the very early years after screening. Other reviews such as the UK review include this, but so do a number of other studies yielding a very different result.
A useful paper for introducing students and junior doctors to the ideas around screening effectiveness, but the results themselves are already well known. With increasing survival due to improved treatment (regardless of mode of detection), it becomes ever harder to demonstrate changes in mortality, and it doesn't necessarily matter because improved survival also means the main impact of screening is likely to be improved morbidity rather than mortality. Should screening still be recommended if it makes no change in survival but avoids a stoma or a mastectomy for the remaining length of life? That is an ongoing knowledge gap and would be the more useful study.
A large study and interesting results that most would not have guessed.
Outstanding and carefully conducted meta-analysis with intention-to-treat outcomes. Good discussion of other competing risks for death.