Screening for colorectal cancer (CRC) substantially reduces deaths and as such, is recommended for those aged between 50 to 75 years-old. Those are the findings of the new report by the U.S. Preventative Services Task Force (USPSTF).

The report also advises that screening for adults aged 76 to 85 years should be an individual choice which takes the patient’s health into account and prior screening history.

Studies from MEDLINE, PubMed, and the Cochrane Central Register of Controlled Trials between 2008 and 2014, were analyzed as part of the report. The new recommendations for screening are in line with those made when the last USPSTF study was published in 2008, despite similar recommendations being in place since 2008, its estimated that in 2012 28% of eligible U.S. adults had never been screened for CRC. This updated study assessed a total of 95 new empirical studies. 

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There are several CRC screening strategies and each has varying levels of evidence to support use, from aims to test acceptability and adherence. The multifaceted nature of testing is compounded by the test quality being more operator-dependent (eg, colonoscopy, CTC).

Robust data from well-conducted population-based screening RCTs have demonstrated that both Hemoccult II and flexible sigmoidoscopy can reduce CRC mortality, however neither of these tests are widely used in the U.S.

Pooled results showed that flexible sigmoidoscopy was associated with lower CRC-specific mortality compared with no screening at 11 to 12 years follow-up (incidence rate ratio, 0.73; 95% CI, 0.49-0.84; I2 = 44%). The SIG trials included for analysis consisting of a total of 485,002 participants.

For stool-based testing, such as guaiac-based fecal occult blood testing (gFOBT), Hemoccult II resulted in a reduction in CRC-specific mortally after 2 to 9 rounds of screening (RR, 0.91; 95% CI, 0.84-0.98, at 19.5 years to RR, 0.78; 95% CI, 0.65-0.93, at 30 years).

For computed tomographic colonography (CTC), the per-person sensitivity to detect adenomas 10mm and larger ranged from 67% (95% CI, 45%–84%) to 94% (95% CI, 84%–98%), and specificity ranged from 98% (95% CI, 96%–99%) to 96% (95% CI, 95%–97%). However, these studies were not powered to estimate test performance to detect CRC.

With regards to adverse effects, the likelihood of harm from screening in adults 50–75 years of age is small; the harms of screening in adults 76 years and older are small to moderate. The majority of harms result from the use of colonoscopy, either as the screening test or as follow-up for positive findings detected by other screening tests.

Although the authors reached a definite conclusion for screening recommendations, they voiced a need for further research into screening strategies, specifically studies of diagnostic accuracy to confirm screening test-performance of stool tests based on high sensitivity to detect CRC.

“Empirical studies, trials, or well-designed cohort studies with average-risk populations are still needed to evaluate programs of screening using colonoscopy, the best-performing stool tests, and effect of CTC on cancer mortality,” they concluded.

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