Nodal Staging Score: A Tool to Assess Adequate Staging of Node-Negative Colon Cancer -- Gönen et al. 27 (36): 6166 -- Journ
Posted Jan 12 2010 12:32pm
Gonen, Schrag and Weiser recently report a study of colorectal cancer patients from the 1994-2005 SEER database to quantify the likelihood that a node-negative patient is, in fact, node-negative. This is an interesting alternative method of assessing adequate staging of CRC in contrast to the usual "one-size-fits-all" minimum lymph node criteria (namely, 12).
They have developed a "nodal staging score" (NSS) that expresses the probability of a patient being "true negative" and find that this score depends on the T stage. Overall, the probability of missing a positive node that is actually present is 29.7% if only 5 nodes are examined; 20.0% if eight are examined; 13.6% if 12 nodes are examined. However, for a NSS of 90% (that is, a 90% likelihood that the patient is truly node-negative), a single node is sufficient for T1 tumors, 4 nodes for T2 tumors, 13 nodes for T3, and 21 nodes for T4.
The authors provide graphical and tabular tools areprovided to facilitate calculation of NSS and treatment decisionmaking for daily clinical practice.
I question whether a 90% likelihood is good enough--I am not comfortable with that at all, especially at the T2 stage. Four nodes just is not adequate and the implications are fairly significant. It would be interesting to re-evaluate the data for NSS at 95% or 97.5%. It seems, interestingly enough, that--at a major critical clinical point, the T3 tumor, the minimum number of nodes (at least for a NSS of 90%) is 13--very close to the current 12-lymph node standard. Biologically, this makes perfect sense in that, intuitively, a node-positive T1 tumor ought to be very uncommon and the burden of proof would definitely be on the pathologist to demonstrate that a patient with a T4 tumor is indeed node-negative (gotta show me more than 12 nodes!).