medwireNews: Some of the most common screening tests for cancer may not extend individuals’ lives, indicate the results of a systematic review and meta-analysis of randomized clinical trials comparing screening with no screening.
Based on data for 2,111,958 individuals from the general population with at least 9 years’ follow-up, the study showed no evidence of a tumor-specific or all-cause mortality benefit with mammography for breast cancer, colonoscopy or fecal occult blood testing (FOBT) for colorectal cancer, computed tomography for lung cancer, and prostate-specific antigen testing for prostate cancer.
The only screening test that significantly increased longevity, when reviewing the relative risk for all-cause mortality but not death from the target cancer, was sigmoidoscopy for colorectal cancer, with a lifetime gain of 110 days versus not undergoing sigmoidoscopy, the researchers report.
Despite their findings, Michael Bretthauer, from the University of Oslo in Norway, and colleagues do not advocate for screening to be “abandoned” and suggest instead that tests with a positive benefit–harm balance “measured in incidence and mortality of the target cancer” may be worthwhile.
They acknowledge that for some individuals, screening means that cancer is prevented or detected at an early stage and their lives are prolonged, whereas others experience a “lifetime loss” caused by harms associated with screening or treatment of screening-detected cancers.
“It might be wise to reconsider priorities and dispassionately inform interested people about the absolute benefits, harms and burden of screening tests that they consider undertaking,” the team recommends in JAMA Internal Medicine.
Bretthauer and colleagues identified 18 randomized clinical trials with 10–15 years’ follow-up that measured cause-specific and all-cause mortality after screening.
The relative risk for all-cause mortality after screening was not significant for any of the tests versus no screening, with an absolute difference in deaths from the target cancer ranging from 0.03 per 100 person–years for prostate cancer to 0.23 per 100 person–years for lung cancer.
Other than for sigmoidoscopy, there were also no significant lifetime gains for the screening tests, with 0 days gained for mammography screening and FOBT (annual or biennially), 37 days for colonoscopy and PSA screening, and 107 days for lung cancer screening only among smokers or former smokers.
A possible cause for the lack of increased longevity may be due to “competing causes of death,” since many of the cancers being screened for “share risk factors with more prevalent causes, such as cardiovascular and metabolic diseases,” suggest the researchers.
Bretthauer et al say that their study “may provide easy-to-understand estimates for prolongation of life attributable to screening that may be used in shared decision-making with individuals who consider undergoing a screening test.”
They add: “Our estimates may also serve to prioritize public health initiatives in comparison with other preventive measures, such as obesity treatment or prevention of cardiovascular disease.”
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