Oncologic outcomes of primary retroperitoneal lymph node dissection (RPLND) for stage II seminoma: Indiana University experience.

e17012 Background: Stage II seminoma is typically treated with radiotherapy or chemotherapy based on NCCN guidelines. Primary RPLND has demonstrated efficacy as first-line therapy for retroperitoneal (RP)-only disease. Our aim was to study recurrences of patients undergoing primary RPLND for Stage IIa or IIb seminoma to identify clinicopathologic factors affecting outcomes. Methods: Using our prospectively maintained database, we identified patients that had primary RPLND for seminoma from 2014-2021. All patients had at least 6 months of follow up. Patients were clinical stage IIa or IIb at the time of surgery and underwent open RPLND. We used Kaplan-Meier analysis for recurrence free survival (RFS) and compared clinicopathologic factors. Results: We identified 67 patients that underwent RPLND for RP only seminoma. Table shows the clinical characteristics of patients experiencing recurrences (median follow up - 22.4 months) and excludes 2 patients that had adjuvant chemotherapy. The 2-year RFS rate was 80.2%. Eleven patients (16.4%) experienced recurrences. Kaplan Meier analysis demonstrated improved survival in patients that had an RPLND after 12 months of surveillance (p = 0.02). Fifty-six patients were presumably cured with surgery alone at time of last follow-up. No patients died of testis cancer. One patient had a recurrence within the surgical field. Two patients had contralateral recurrences that may have been cured with bilateral RP template dissection. Seven patients that had a bilateral template dissection had disease on the contralateral side, of which 4 patients had visible nodes on pre-operative scans. In total, 9 out of 67 patients had disease on the contralateral side suggesting that bilateral RP template could confer higher cure rates. Recurrences were successfully treated with BEPx3 (9 pts), Redo RPLND then BEPx3 (1 pt), BEPx3 then High Dose chemotherapy (1 pt), and EPx4 (1 pt). Conclusions: Primary RPLND for low volume RP disease is effective with over 80% chance of surgical cure. Recurrences were cured almost exclusively with induction chemotherapy. Patients with delayed RP only recurrences had improved surgical success. Further investigation in larger trials may help standardize bilateral templates in seminoma and surveillance protocols in the post-operative setting. [Table: see text]