Incidence of cancer in patients with large colorectal polyps lower than previously thought

The screening for and removal of precancerous polyps during colonoscopy is largely responsible for the decrease in incidence rates of colorectal cancer among Americans. However, a significant proportion of people who undergo colonoscopies have large polyps considered too challenging to be removed endoscopically. In such cases, these patients are referred for surgical resection to remove the polyps.

"Currently a majority of patients undergo colon resections for large polyps that don't harbor any cancer cells, which means in many cases a person's colon is being removed for noncancerous reasons, based on subjective criteria," said lead study author Emre Gorgun, MD, FACS, FASCRS, a staff surgeon in the department of colorectal surgery, Cleveland Clinic, Ohio.

For the study, Dr. Gorgun and his colleagues aimed to evaluate the actual incidence of invasive cancer in patients referred for surgical resection of large, apparently benign colorectal polyps.

In this single center, retrospective study at Cleveland Clinic, investigators reviewed the medical records of 439 patients who underwent colectomy over a 15-year period. The colorectal polyps were considered too difficult for standard endoscopic treatment. The decision to treat a polyp endoscopically depends on multiple factors including polyp size, risk of bleeding and perforation (the colon wall is thin and can be ruptured easily), difficult location and endoscopist's discretion.

All patients included in this study had polyps that were not diagnosed as cancer prior to their surgical procedures. During a colonoscopy, the polyp, which may appear to be benign (for example, it has a soft consistency), is removed and the tissue is sent to a pathologist for biopsy confirmation.

In total, cancer was identified in the final pathology in just 37 patients. "The significant finding of this research is that only 8 percent of patients who underwent colectomy for a large, apparently benign polyp had cancer, which means that 92 percent of patients had their colon removed for noncancerous reasons," Dr. Gorgun said. "But colon resection doesn't come for free--it's a major abdominal operation associated with the risk of serious adverse events."

The complication rate after colorectal procedures was nearly 20 percent in the study. In total, 83 patients developed complications within 30 days postoperatively, and complication rates were similar between the noncancerous and cancerous groups.

"Our study is a real eye opener; it's the first step showing the low incidence of cancer in these large polyps, which is not as previously thought," Dr. Gorgun said.

In addition to improving the quality of life for patients and the cost benefit to health care systems, treating these types of polyps with more advanced endoscopic techniques could avoid many complications. The more advanced techniques include two procedures called endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD).

However, these advanced endoscopy procedures and other advanced approaches that combine endoscopy and laparoscopy require physicians with specialized skill and training. The good news is that experienced physicians are able to successfully treat these large, technically difficult polyps without sacrificing the colon.

"These findings suggest that we need to transform our surgical approach to ensure we better serve each patient. In a patient with an endoscopically unresectable colorectal polyp that looks benign, a more conservative, organ-sparing approach to removing them is usually safe," Dr. Gorgun said. "Our results suggest that advanced endoscopic techniques or a laparoscopic-assisted approach should be considered if there is not high suspicion for cancer."

The study authors noted that the major limitations of the study are its retrospective nature and the long time interval over which it occurred. Many medical and technical advances have developed over the last decade. Still, the authors conclude that the number and uniformity of the patient population in this study make it possible to comment on the risk of undiagnosed cancer in apparently noncancerous colorectal polyps and the consequences of not making that diagnosis preoperatively.