The length of patient survival, after colon cancer surgery, has been
generally associated with the specific number of lymph nodes.
This examination of number of lymph nodes has been a quality indicator for hospitals. A study in the November issue of JAMA has expressed doubts about this and stated that the number of lymph nodes may not be linked to patient survival.
Sandra L. Wong, M.D., M.S., of the University of Michigan, Ann Arbor, and colleagues, using data from the national Surveillance Epidemiology and End Results (SEER)-Medicare linked database (1995-2005), assessed whether hospitals' lymph node examination rates were associated with cancer staging, use of adjuvant (supplemental) chemotherapy (indicated for patients with node-positive disease), and 5-year survival. The study included 30,625 patients undergoing colectomy for nonmetastatic colon cancer. Hospitals were ranked according to the proportion of their patients in whom 12 or more lymph nodes were examined and then were sorted into four groups. Late survival rates were assessed for each hospital group, adjusting for potentially confounding patient and clinician characteristics.
Hospitals with the highest proportions of patients with 12 or more lymph nodes examined tended to treat lower-risk patients and had substantially higher procedure volumes. After adjusting for these and other factors, there remained no statistically significant relationship between hospital lymph node examination rates and survival after surgery. Although the four hospital groups varied widely in the number of lymph nodes examined, they were equally likely to find node-positive tumors. There were no clinically important differences in the use of adjuvant chemotherapy, either overall (unadjusted rates of 26 percent for the highest hospital quartile vs. 25 percent for the lowest hospital quartile) or within cancer stage subgroups.
"Our study raises questions about the importance of examining a large number of lymph nodes in patients with colon cancer," the authors write.
Regarding the finding of no evidence of higher 5-year survival at hospitals with higher lymph node examination rates: "Our analyses also suggest a simple explanation for these null findings. Regardless of how many lymph nodes hospitals examined, they tended to find the same number of node-positive ones. As a result, higher hospital lymph node examination rates did not result in greater detection of patients with node-positive tumors or higher rates of adjuvant chemotherapy."
"Using lymph node counts as a hospital quality indicator is gaining momentum from stakeholders in the health care community," the researchers write. "The number of lymph nodes hospitals examine following colectomy for colon cancer is not associated with staging, use of adjuvant chemotherapy, or patient survival. Efforts by payers and professional organizations to increase node examination rates may have limited value as a public health intervention."
(JAMA. 2007;298(18):2149-2154. Available pre-embargo to the media at www.jamamedia.org)