Impact of socioeconomic status on extent of lymph node dissection for colon cancer

Background: The pathologic identification of 12 or more lymph nodes (LN) after colectomy for colon cancer became a quality indicator for surgery in 2001. We investigated whether this new standard of care was differentially adopted across racial and socioeconomic lines. Methods: We identified 111,339 stage I to III colon cancer patients identified as black or white in the Surveillance, Epidemiology, and End Results database from 1988 to 2004 who underwent colectomy. We did multivariable logistic regression to investigate the influence of race, area socioeconomic status (SES), and other clinical and demographic characteristics on the number of LNs examined. Results: Between 1988 and 2004, white patients were more likely than black patients to have ≥12 LNs identified (odds ratio, 1.06; 95% confidence interval, 1.02-1.10) after adjustment for age, year of diagnosis, sex, marital status, tumor grade, stage, and subsite within the colon. After adjustment for SES, race was no longer significant (adjusted odds ratio, 1.00; 95% confidence interval, 0.96-1.04). There was, however, a significant positive trend between a patient's SES and having ≥12 LNs examined (P_trend < 0.0001), with a 30% increased odds comparing the highest to the lowest quintiles of SES. We found that the association between SES and the dissection of ≥12 LNs was only present in individuals diagnosed after 1999. Conclusions: The association between high SES and the examination of ≥12 LNs was only apparent from 2000 onward, and coincides with its dissemination and acceptance as a new standard of care. This suggests that the emergence of LN dissection as a quality indicator may have been more rapidly disseminated into higher SES groups.