Lymph node dissection technique is more important than lymph node count in identifying nodal metastases in radical cystectomy patients: a comparative mapping study.

Background: The value of lymph node dissection (LND) in the treatment of bladder urothelial carcinoma is well established. However, standards for the quality of LND remain controversial.

Objective: We compared the distribution of lymph node (LN) metastases in a two-institution cohort of patients undergoing radical cystectomy (RC) using a uniformly applied extended LND template.

Design, Setting, And Participants: Patients undergoing RC at the University of Southern California (USC) Institute of Urology and at Oregon Health Sciences University (OHSU) were included if they met the following criteria: (1) no prior pelvic radiotherapy or LND; (2) lymphatic tissue submitted from all nine predesignated regions, including the paracaval and para-aortic LNs; (3) bladder primary; and (4) category M0 disease. The number and location of LN metastases were prospectively entered into corresponding databases.

Measurements: LN maps were constructed and correlated with preoperative and pathologic characteristics. Kaplan-Meier curves were constructed to estimate overall survival (OS) and recurrence free survival (RFS) among LN-positive (LN+) patients.

Results And Limitations: Inclusion criteria were met by 646 patients (439 USC, 207 OHSU), and 23% had LN metastases at time of cystectomy. Although there was a difference in the median per-patient LN count between institutions, there were no significant interinstitutional differences in the incidence or distribution of positive LNs, which were found in 11% of patients with ≤pT2b and in 44% of patients with ≥pT3a tumors. Among LN+ patients, 41% had positive LNs above the common iliac bifurcation. Estimated 5-yr RFS and OS rates for LN+ patients were 45% and 33%, respectively, and did not differ significantly between institutions.

Conclusions: LN metastases in regions outside the boundaries of standard LND are common. Adherence to meticulous dissection technique within an extended template is likely more important than total LN count for achieving optimal oncologic outcomes.