(Ivanhoe Newswire) -- The number of lymph nodes evaluated for colon cancer has risen significantly over the past two decades. However, according to a study in the September 14 issue of JAMA, this improvement is not associated with an increase in node-positive cancers.

"Among patients surgically treated for colon cancer, several studies have demonstrated better survival for patients with more lymph nodes evaluated," according to background information in the study.

The article goes on to say, "The proposed mechanism behind this association suggests that a more extensive lymph node evaluation reduces the risk of understaging, in which inadequate assessment may incorrectly identify a patient with node-positive disease as node-negative, thus failing to identify appropriate treatment."

Most organizations and consensus panels advocate surgical evaluation of 12 or more lymph nodes for staging newly diagnosed colon cancer patients. However, some researchers are questioning this process.

"Recently, some studies have questioned the understaging mechanism, suggesting that efforts by payer and professional associations to increase the number of lymph nodes evaluated during colon cancer surgery may have a limited role in improving survival," the authors write.

Helen M. Parsons, M.P.H., of the National Cancer Institute, Bethesda, Md. and colleagues looked at data from the Surveillance, Epidemiology, and End Results (SEER) program from 1988 through 2008 to examine trends in the degree of lymph node evaluation for colon cancer and how they are associated with survival.

The researchers found that lymph node evaluation for colon cancer increased tremendously from 1988 to 2008. 34.6 percent of patients received evaluation of 12 or more lymph nodes in 1988, that number had risen to 73.6 percent by 2008.

While the number of lymph nodes evaluated increased significantly, the number of node-positive cancers diagnosed did not. 40 percent of patients were diagnosed with node-positive cancer in 1988, and just 42 percent in 2008.

Although patients with a high number of lymph nodes evaluated were only slightly more likely to have node-positive disease, they did experience significantly lower relative hazard of five-year death in comparison to those with fewer nodes evaluated.

The authors conclude, "The number of lymph nodes evaluated for colon cancer markedly increased in the past two decades but was not associated with an overall shift toward higher-staged cancers, questioning the upstaging mechanism as the primary basis for improved survival in patients with more lymph nodes evaluated."

SOURCE: JAMA, published online September 14, 2011