Limitations of lymph node counts as a measure of therapy

For several cancers, the number of lymph nodes removed during surgery is associated with survival. Observational studies supporting this association have prompted considerable debate regarding the extent of lymphadenectomy, and in some dieases, absolute lymph node counts have been suggested as a measure of the quality of cancer care. However, for most cancers, lymph node counts may not directly influence survival in a causal manner. In fact, several randomized clinical trials addressing the question in lung, gastric, and pancreatic cancers have not shown more extensive lymph node dissections to be linked with improved survival. Despite this negative evidence, however, lymph node counts have remained a target process in quality initiatives. Misinterpretation of the evidence may be driving some of the pressure to broadly implement more extended lymph node dissections. As a process for more accurate disease staging and as a potential marker for the completeness of surgery, lymph node counts are likely linked to quality, at least indirectly. However, a causal association between lymph node counts (and extented lymphadenectomy) and survival is tenuous and has not been supported by high-level evidence.