These tumors are the ones most likely to be diagnosed through a screening program for many reasons: they are fairly common, the cure rates of surgery may exceed 90% if treated in early stages and, finally, in most cases evolve from premalignant lesions (polyps) that can be removed to prevent cancer progression.
Evidence of early diagnosis in the population
The most common is the detection of fecal occult blood (searching for blood in the stool that is not detected by the naked eye). The first drawback is the need to collect feces, but the main one is its imprecision. When the test is positive there is a 10% chance that the individual has cancer and 34% of this a polyp. Unfortunately, the test will be negative in up to 50% of patients with cancer (this percentage drops to 30% if repeated for 3 consecutive days).If the result is positive, then needed a colonoscopy. The test is therefore not optimal given that the high rate given positive tests (FOBT) in patients who do not actually have cancer (false positive) will be therefore a negligible percentage of people they will be subjected to an annoying and unnecessary examination, colonoscopy, when in fact they are free of such disease.
However, some research has shown that if you perform a test of annual fecal occult blood testing to all individuals above 50 years would be reduced by one-third of colorectal cancer deaths. This result seems interesting, in fact, this test is usually recommended in the United States. The rising cost of living one year survival is about $ 45,000 (approx. 8 million pesetas), which is well beyond the reach of most health systems. Furthermore, only 3% of the population (excluding high-risk individuals) will die from colorectal cancer being diagnosed at an average age of 65, with a life expectancy of about 10 years. Therefore, the average survival gain for an individual, if all colorectal cancer deaths were prevented, would be 3% of 10 years, which corresponds to 4 weeks.
If one third of deaths could be avoided obtained survival would be 5 weeks. Moreover, the benefit would be lower in people who have healthy lifestyles, which consume large quantities of vegetables and exercise. Therefore, the institutions of the European health systems like ours underestimate the dubious advantages of a massive program of preventive diagnosis of colorectal cancer in the general healthy population.
Are currently conducting studies to investigate the effectiveness of the determination of fecal occult blood and sigmoidoscopy (colonoscopy of the last sections of the colon), where there are more tumors. In theory, flexible sigmoidoscopy is a better screening test because it can better detect precancerous lesions and colon polyps, but is handicapped in its invasiveness and the possibility of leaving undiagnosed tumors located above the area to the best of the endoscope . In the United States and Japan has proposed the use of routine colonoscopy as part of an early diagnosis together with evidence of occult blood in feces. Not all experts agree with this proposal, but it seems prudent to await the results of more current research before introducing a colonoscopy as part of screening for colorectal cancer in healthy people.
credit to: Dr. Julio Mayol MartÃnez, Dr. Jonathan Rhodes
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