Clinical Question: Does fecal occult blood testing (FOBT) reduce all-cause mortality?

Setting: Population-based

Study Design: Meta-analysis (randomized controlled trials)

Allocation: Uncertain

Synopsis: The idea behind screening tests is that they may detect something in otherwise healthy persons that will help them live longer, making all-cause mortality the most important outcome measure of any screening. This study tried to determine if FOBT reduces all-cause mortality. The authors combined data from three large published randomized trials of FOBT: one Danish, one British, and one American. All studies compared FOBT, performed every two years, with no screening.

The British and Danish studies used unrehydrated FOBT in adults 45 to 75 years of age; the American study used rehydrated FOBT in adults 50 to 80 years of age. All three studies monitored patients for a mean of 12 years; which means that 245,217 persons were followed up for more than 3 million patient years. Overall, there was a 13 percent relative reduction in colorectal cancer mortality. In absolute terms, dividing the total colorectal cancer deaths by total participants, that is 0.82 versus 0.94 percent (P = .002; number needed to treat = 833 for 12 years).

There was a 1.9 percent relative increase in noncolorectal cancer deaths in the non-screened group, and no overall difference between groups in all-cause mortality (26.51 for screened and 26.46 for nonscreened patients). Potential explanations for this paradox include unintended consequences of screening (e.g., failure of the patient to adopt a healthier lifestyle because he or she has been screened, mortality from follow-up colonoscopy) and better identification of colorectal cancer as a cause of death in screened patients.

Bottom Line: Screening for colorectal cancer using FOBT does not reduce all-cause mortality. This is important when considering whether to screen healthy patients. (Level of Evidence: 1a)