A study in the September 14 issue of JAMA revealed, that the increase in the percentage of patients who have a high number of lymph nodes evaluated during colon cancer operations has increased significantly during the past two decades, however, this improvement is not linked to an increase in the overall proportion of colon cancers that are node positive.
According to background information in the article: "As wide-ranging quality improvement efforts emerge throughout the health care system, finding mechanisms for optimizing cancer care through accurate staging and appropriate treatment has become an area of substantial interest to policy makers. Among patients surgically treated for colon cancer, several studies have demonstrated better survival for patients with more lymph nodes evaluated. 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 practice organizations and consensus panels currently support the surgical evaluation of 12 or more lymph nodes for acceptable staging of newly diagnosed colon cancer patients. According to the authors:
"Recently, some studies have questioned the understaging mechanism, suggesting that efforts by payers and professional associations to increase the number of lymph nodes evaluated during colon cancer surgery may have a limited role in improving survival."
Helen M. Parsons, M.P.H., of the National Cancer Institute, Bethesda, Md. and her team assessed trends in lymph node evaluation degrees for colon cancer and their associated link with survival by analyzing data from the Surveillance, Epidemiology, and End Results (SEER) program, from 1988 to 2008, including 86,394 patients who had surgery for colon cancer.
They discovered that lymph node evaluation for colon cancer increased significantly from 1988 to 2008. From 1988 to 1990, 34.6 percent of patients (n = 3,875) received lymph node evaluation at a level of 12 lymph nodes or more. Between 1994 and 1996, 37.9 percent of patients (n = 4,362) equaled this evaluation level, increasing to 46.8 percent in 2000 to 2002 and 73.6 percent (9,798/13,310) respectively from 2006 to 2008. Although the number of lymph nodes evaluated increased significantly, there is no link to an increase in node-positive cancers over this period (40 percent in 1988-1990, 42 percent in 2006-2008).
The authors also discovered that even though patients with high rates of lymph node evaluation had only a marginally higher chance of having node-positive disease, they experienced a substantially lower relative risk of 5-year mortality compared with those with fewer nodes evaluated.
"When stratified by node positivity, patients with node-positive disease as well as node-negative disease continued to experience lower relative hazard of death when more lymph nodes were evaluated. In conclusion, the number of lymph nodes evaluated for colon cancer markedly increased in the past 2 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."
An accompanying editorial by Sandra L. Wong, M.D., M.S., of the University of Michigan, Ann Arbor, Mich., states that the findings of this study suggest a questionable use of some quality indicators.
"One of the major hazards associated with the development and implementation of quality indicators is the lack of association with outcomes because the mechanisms by which adherence to certain processes of care lead to improved outcomes are unclear. What is clear, however, is that seemingly straightforward associations between processes of care and improvements in outcomes are not easily understood and these relationships may not be causal. 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 study by Parsons et al further questions the utility of this indicator."
Written by Petra Rattue