Purpose: The role of lymph node dissection is still controversial in patients treated with radical nephroureterectomy for upper tract urothelial cancer. We developed a pathological nodal staging model that allows quantification of the likelihood that a patient with pathologically node negative disease has, indeed, no lymph node metastasis. Materials and Methods: We analyzed data on 814 patients treated with radical nephroureterectomy and lymph node dissection, and estimated the sensitivity of pathological nodal staging using a β-binomial model. We developed a pathological nodal staging score that represents the probability that a case is correctly staged as node negative. Results: A median of 5 lymph nodes (range 1 to 46) was removed and 593 patients (73%) had pN0 disease. The probability of missing lymph node metastasis decreased as the number of nodes examined increased. If only a single node was examined, 44% of patients would have been misclassified as having pN0 disease while harboring lymph node metastasis. Even when 5 nodes were examined, 12% of patients would have been misclassified. The proportion of those with a positive node increased with advancing pathological T stage and lymphovascular invasion. Patients with pT0-Ta-Tis-T1/lymphovascular invasion had more than a 95% chance of correct pathological nodal staging with 2 examined nodes. However, if a patient had pT3-T4 and positive lymphovascular invasion, even 20 examined lymph nodes did not attain 95% accuracy. Conclusions: Lymph node dissection provides more accurate staging and prediction of survival. The number of examined nodes needed for adequate staging depends on pT stage and lymphovascular invasion. We developed a tool to estimate the likelihood of false-negative lymph node metastasis, which could help refine clinical decision making regarding the administration of adjuvant chemotherapy.
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