english.prescrire.org > Spotlight > Archives : 2012 > Immunoassay-based screening for colorectal cancer: cancers detected, at the cost of colonoscopy-related complications

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Immunoassay-based screening for colorectal cancer: cancers detected, at the cost of colonoscopy-related complications

Compared with the traditional Haemoccult° test, immunochemical tests seem to improve colorectal cancer screening. But they double the number of colonoscopies carried out, increasing the number of colonoscopies with no lesions detected and the number of colonoscopy-related complications.

Organised screening for colorectal cancer has been general practice in France since 2002. Offered every two years to adults aged between 50 and 74, this screening consists of identifying blood in the stools using the Haemoccult° test, followed by a colonoscopy if the test gives positive results. The Haemoccult° test gives false negative results in 50% of cases and is therefore not very sensitive.

In 2011, the French national colorectal cancer screening programme recommended replacing Haemoccult° tests with more sensitive machine-readable immunochemical tests.

According to comparisons with the Haemocult° test, immunochemical tests permitted the detection of twice the number of colorectal cancers and three times the number of precancerous adenomas. But they double the number of colonoscopies, without increasing the cancer detection rate. For both types of test, one cancer is detected for around 14 colonoscopies carried out.

Colorectal cancer screening exposes patients to the adverse effects of colonoscopy. Around 3 cases of severe complications arise per 1000 colonoscopies, especially perforations and haemorrhages.

Direct comparison of the performances of the various immunoassay-based tests is an important factor in determining whether immunochemical tests really improve the harm-benefit balance of colorectal cancer screening regarding both the gain in terms of reduced colorectal cancer mortality and the frequency of colonoscopy-related complications.

©Prescrire 1 December 2012

"Immunoassay-based screening for colorectal cancer" Prescrire Int 2012; 21 (133): 299-302. (Pdf, subscribers only)
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