Lymph Node Examination Rate, Survival Rate, and Quality of Care in Colon Cancer

To the Editor: In their study examining the association of hospital nodal evaluation rates and survival after colectomy for cancer, Dr Wong and colleagues¹ concluded that examination of increasing numbers of lymph nodes is not associated with survival at the hospital level and that evaluation of 12 or more lymph nodes is not a useful quality measure.

However, their data actually demonstrate a significant improvement in survival in a key population. Table 3 shows a survival advantage for stage II patients treated at hospitals with high lymph node examination rates (adjusted hazard ratio, 0.85; 95% confidence interval, 0.74-0.96). The patients who would benefit most from having 12 or more nodes examined are stage II patients who have had an inadequate number of lymph nodes examined to confidently deem them free of nodal metastases. These understaged patients would fail to receive the potentially lifesaving benefits of adjuvant chemotherapy.² When examined in a single model combining all stage groups, the benefit of examining increasing numbers of nodes is diluted by the lesser effect in stage 0, I, and III patients. Lymph node evaluation is so poor nationally that in the hospitals with the highest nodal examination rates, the median is only 13 nodes (Table 1), leaving more than 25% of patients at these hospitals potentially understaged and further blunting the potential survival benefit expected in a group of patients who all have 12 or more nodes examined.

The measure requiring examination of 12 or more nodes was endorsed by the National Quality Forum as a quality surveillance indicator.³ It is intended to be used by hospitals to spark internal quality improvement initiatives, not as a basis for reimbursement decisions or holding individual clinicians accountable. Moreover, it is unlikely that there is any quality measure for which there is perfect evidence. It is potentially of equal or greater danger to fail to advance reasonable indicators, especially those intended for quality surveillance. Quality measure development is an iterative process. Even measures based on high-level evidence will become outdated or be modified over time with scientific advances.

Lymph nodes must be examined to accurately stage colon cancers and guide adjuvant treatment decisions. Not establishing a benchmark would legitimize examining only a few lymph nodes, which would clearly be deleterious. Some nodal evaluation threshold must be set, particularly when a survival advantage has been identified.^{1 ,4 - 5} Monitoring lymph node examination rates for colon cancer is probably a worthwhile measure of quality.