Colonoscopy is considered the gold standard for screening for colon polyps and cancer. It is recommended and paid for by many third payor parties including Medicare. Few people realize that there is paucity of randomized trials supporting the benefit of colonoscopy Few realize that there has been paucity of direct evidence in support of concept that colonoscopy would help reduce colon cancer and its resultant morbidity and mortality.
Current estimates of the effect of colonoscopy on CRC incidence—an estimated reduction of 76% to 90% reduction of incidence colon cancer as a result of colonscopy is based on data from national polyp study which lacked concurrent controls.
However, recently a few studies have cast a doubt on the presumed effectiveness of colonoscopy with respect to reducing risk of right sided colon cancers. This was supposed to be the advantage of colonoscopy over sigmoidoscopy.
Brenner and colleagues wished to determine if a prior colonoscopy compared with no colonoscopy was associated with reduced prevalence of advanced colorectal neoplasms (defined as cancers or advanced adenomas).This population based study involved a statewide cross-sectional study of 3287 subjects 55 years or older from Germany. Prevalence of advanced colorectal neoplasms was assessed by screening colonoscopy and histopathologic examination of the lesions.
Advanced colorectal neoplasms were found in 11.4% of the 2701 subjects without prior colonoscopy as compared 6.1% who had undergone colonoscopy within the preceding 10 years. Overall and site-specific adjusted prevalence ratios for previous colonoscopy demonstrated that the colonoscopy in the prior 10 years was associated with a reduction in prevalence of left-sided advanced colorectal neoplasms, but not right-sided advanced neoplasms.
Another study was performed by Baxter and colleagues. They conducted a population-based, case-control study to examine the effectiveness of colonoscopy for preventing deaths related to colorectal cancer in Ontario, Canada. The authors identified 10, 292 case patients and 51, 460 controls from administrative claims data. 7.0% of patients and 9.8% of the controls had previously undergone a colonoscopy. Logistic regression showed that colonoscopy was significantly associated with fewer deaths from left-sided colorectal cancer (Odds ratio 0.33; C.I. 0.28 to o.39) but not from right-sided colorectal cancer.
Above studies may call into question the beneficial value of colonoscopy for colorectal cancer screening. Ranshoff argues that based on these data, we should probably tell our patients that high quality colonoscopy results in a 60% to 70% reduction iof the risk for death from colorectal cancer as opposed to 90% reduction that has been largely assumed.
Above Ranshoff suggestion notwithstanding, an even more important question may be whether the widespread use of colonoscopy as the screening method is actually a cost-effective versus a grossly wasteful method of screening. Colonoscopy has a much higher risk for significant complications as compared to other cancer screening modalities. An extreme view might be that colonoscopy as a primary tool of colon cancer screening is a misuse of health care dollars and that flexible sigmidoscopy should suffice in average risk subjects.
Obviously, such confusion and controversy has occured because of the use of colonoscopy based on indirect data and now we have poulation based studies challenging the degree of its effectivensss. Only large randomized controlled trials can help answer these vexing questions.
In the emantime, is there a significant incremental benefit of colonoscopy over flexible sigmoidoscopy for colorectal cancer screening? Is the magnitude of increased benefit from colonoscopy as compared to flexible sigmoidoscopy sufficient to justify the huge increase in cost, not to mention the additional risk for complications.
Baxter and Rabeneck argue that as more observational evidence accumulates, the answer to this question becomes less certain. Is it time to set up an expert panel to re-examine the issue whether the colonoscopy offers substantial benefit over flexible sigmoidoscopy in a cost effective manner.
What are your views on the above studies and resultant cdontroversy? please share your thoughts.