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Colon cancer staging not changed with increased lymph node evaluation

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – A large increase in the number of lymph nodes evaluated during surgery for colon cancer — a quality improvement metric– has not had any great effect on the percentage of node-positive cancers found, according to a report in the Journal of the American Medical Association for September 14.

“The quality indicator of counting more than 12 lymph nodes per resected colon cancer specimen does not directly measure a process that by itself improves outcomes,” the author of an accompanying editorial concludes.

In their report, Dr. Helen M. Parsons, with the National Cancer Institute in Bethesda, Maryland, and colleagues explain that the survival of colon cancer patients undergoing surgery is known to be better when more lymph nodes are evaluated — presumably by reducing the risk of understaging. Evaluation of 12 or more lymph nodes for staging of newly diagnosed colon cancer patients is widely recommended.

To further investigate the association between lymph node evaluation and survival, the team analyzed 20-year data in the Surveillance, Epidemiology, and End Results (SEER) program on 86,394 patients surgically treated for colon cancer.

The percentage of patients having 12 or more lymph nodes evaluated more than doubled between 1988 and 2008, from 34.6% to 73.6% (p<0.001), the researchers found. However, this did not lead to any great degree of upstaging; the change in the proportion of node-positive cancers over time, from 40% to 42%, was not significant (p=0.53).

Only slightly more node-positive cancers were detected in patients having 30-39 nodes examined compared to those having 1-8 nodes evaluated (odds ratio 1.11). Nonetheless, the extensively evaluated group had a lower risk of death (hazard ratio 0.66), according to the report.

“These findings suggest that other factors besides upstaging, such as improved surgical quality or postsurgical care, may be the driving mechanism behind the lymph node–survival relationship,” Dr. Parsons and colleagues conclude. “As a result, implementing wide-range quality improvement initiatives to increase lymph node evaluation for colon cancer may have a limited effect on improving survival in this population.”

As Dr. Sandra L. Wong, of the University of Michigan, Ann Arbor, comments in her editorial, “Seemingly straightforward associations between processes of care and improvements in outcomes are not easily understood and these relationships may not be causal.”

JAMA 2011; 306:1089-1071,1140-1141.