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.