Colonoscopy Should Be Targeted at High-Risk Patients

Becky McCall

July 01, 2010

July 1, 2010 — Surveillance colonoscopy should target individuals with high risk for colorectal cancer who are most likely to benefit, according to a new study published in Gastroenterology.

Headed by Sameer Dev Saini, MD, MS, clinical lecturer in the Department of Internal Medicine, University of Michigan, the study examined the cost-effectiveness of various surveillance strategies and concluded that overuse of colonoscopy as a surveillance tool aimed at decreasing the burden of colorectal cancer can be excessively costly, and even harmful.

The American College of Gastroenterologists currently recommends that patients with colonic adenomas undergo surveillance colonoscopy every 5 to 10 years, but Dr. Saini questioned whether this strategy made health-economic sense.

"Guidelines already state that low-risk patients should undergo surveillance every 5 to 10 years, which is congruent with our results. However, 10-year intervals are not frequently used in clinical practice. Our study suggests that, for low-risk patients, a 10-year interval is probably reasonable, and that a 3-year interval is too aggressive," he told Medscape Medical News.

Assessing cost-effectiveness from the perspective of a long-term payer, Dr. Saini and colleagues developed a Markov model to study various surveillance strategies. They used data from a cohort of 50-year-old patients with newly diagnosed adenomas, following them until death. Thirty percent of the population was assumed to be at high risk for colorectal cancer. Costs, quality-adjusted life-years, and incremental cost-effectiveness ratios were measured.

Three strategies that differed by frequency of colonoscopy were compared. "As expected, we found that more frequent surveillance resulted in fewer cancers and cancer-related deaths," wrote the study authors.

A 3/5 strategy, with high-risk screening every 3 years and low-risk screening every 5 years, resulted in 5 fewer cancers and 1 fewer cancer-related death per 1000 patients when compared with a 3/10 strategy (a 3-year screening interval for high-risk patients and a 10-year interval for low-risk patients).

Reducing the low-risk screening interval from 5 to 3 years resulted in 2 fewer cancers and 1 fewer cancer-related death per 1000 patients entering surveillance.

However, Dr. Saini's analysis showed that lives saved through more-frequent colonoscopy came at increased cost, as well as potential harm to quality of life.

On balance, the study suggests that the 3/10 strategy is the optimal strategy in most clinical circumstances, although a 3/5 strategy may apply in some populations in which a low-risk subgroup cannot be reliably identified or if the miss rate for advanced adenomas is thought to be high (at least 14%).

"Frequent colonoscopy [3-year screening] should probably be reserved for high-risk patients. In low-risk patients, no surveillance (10-year screening) is the most cost-effective strategy. From a policy perspective, even 5-year colonoscopy in low-risk patients could be excessively costly," he said.

We need to focus our efforts on high-risk patients.

The authors call for improvements in risk stratification so that surveillance is targeted at those patients most likely to benefit from this practice.

Dr. Saini commented that the evidence suggests that there is currently an overuse of colonoscopy in low-risk patients and an underuse of colonoscopy in high-risk patients. "We need to focus our efforts on high-risk patients, who have the most to gain from these procedures," he said.

In Agreement With American Gastroenterological Association Guidelines

Approached for an independent comment, John M. Inadomi, MD, AGAF, chair of the American Gastroenterological Association's Clinical Practice & Quality Management Committee and director of San Francisco General Hospital, California, said he was supportive of Dr. Saini's results.

"The overall movement we now see is to lengthen the surveillance interval in appropriate patients. Some 10 to 15 years ago, someone with an adenomas polyp would have surveillance colonoscopy every year, but that's expensive and detracts from daily life — it's unpleasant. So basically, this analysis gives us reason to believe that a trend towards a longer interval for low-risk patients is appropriate without doing a real 20-year study."

He continued, "I think in the past, people with adenomas polyps have been lumped together and screened at the same interval. However recent guidelines propose stratification into low-risk (1 or 2 small polyps less than 1 cm in diameter) and high-risk (>3 polyps of 1 cm or more in diameter), or patients who have dysplasia or cancer, or even tubular or villous adenomas.

"This study is about reserving early surveillance for those we believe are highest risk, rather than people we believe are not highest risk in terms of imminent development of cancer. So there's a shift in thinking in that not all adenomas are the same thing, and only if you have a high-risk adenoma should we be doing intensive surveillance," Dr. Inadomi commented.

"American Gastroenterological Association guidelines already propose that low-risk patients be screened every 5 to 10 years. So Dr. Saini's findings say 10 years is most cost-effective, 5 years may give a slight benefit but at more cost, and high-risk lesions should be screened every 3 years. So he confirms what the American Gastroenterological Association has recently produced," he said.

"With all these cost-effectiveness analyses for any type of cancer there is an interesting function of cost effect. The first time you do an intervention — screening or whatever — you get a reasonable return or bang for your buck. This is because the amount able to be detected by screening gets less and less with time, and the shorter the interval, then the less cost-effective it will be. It would be interesting to look at 5/10, 5/5, 5/3 intervals, so looking at the high-risk patients every 5 years rather than 3. My prediction would be that they'd find this cost-effective, and 3 years would have been only marginally more effective at increased cost," Dr. Inadomi commented.

"Also, all these analyses assume high-quality colonoscopies, but a lot of literature shows the practice of colonoscopy is not uniform, so cancers on the right side, for example, may grow faster or are more difficult to detect, and so on. So this analysis assumes optimal colonoscopies, but this does not happen consistently," he added.

Dr. Saini has disclosed no relevant financial relationships. Dr. Inadomi reports receiving funding from the National Institutes of Health to investigate cancer screening but has no industry affiliations or other financial disclosures.

Gastroenterology. 2010;138:2292-2299. Abstract

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