Unilateral or Bilateral Retroperitoneal Lymph Node Dissection in Nonseminoma Patients with Postchemotherapy Residual Tumour? Results from RETROP, a Population-based Mapping Study by the Swedish Norwegian Testicular Cancer Group

Background: The distribution of retroperitoneal lymph node metastases for patients with nonseminoma and a residual tumour of 10-49 mm in a population-based setting is unknown. This information is needed to justify selection of patients for a unilateral template resection. Objective: To describe the location of retroperitoneal metastases and recurrences in patients with nonseminoma germ cell tumour (NSGCT) with a residual tumour of 10-49 mm. Design, setting, and participants: RETROP is a population-based prospective observational mapping study of 213 patients in Sweden and Norway with a retroperitoneal residual tumour of 10-49 mm who underwent postchemotherapy retroperitoneal lymph node dissection for metastatic NSGCT during 2007-2014 with median follow-up of 100 mo. Patients were classified according to the testis primary tumour and the distribution of unilateral or bilateral lymph node metastases (with reference to the aorta) present on pre- and/or postchemotherapy computed tomography (CT) scans. Outcome measurements and statistical analysis: The distribution and rate of teratoma or cancer in unilateral or bilateral retroperitoneal fields and the location and rate of retroperitoneal recurrence were measured. Results and limitations: In total, 65% of the patients had unilateral retroperitoneal lymph node metastases (RLNMs) on CT scans. Patients with unilateral RLNMs had a low risk of contralateral teratoma or cancer (1.6% for right- and 2.6% for left-sided NSGCT) or retroperitoneal recurrence (0% for right- and 4% for left-sided NSGCT). A weakness of the study is that the pathology specimen could not be fully designated to one specific area for some of the patients. Conclusions: Men with postchemotherapy residual disease of 10-49 mm and unilateral metastases on pre- and postchemotherapy CT scans have a low risk of contralateral disease and should be considered for a unilateral template resection. Patient summary: The surgeon can use computed tomography (CT) scans in deciding on the extent of lymph node dissection in patients with testicular cancer. (c) 2021 European Association of Urology. Published by Elsevier B.V. All rights reserved.