Retroperitoneal Nodal Distribution for Metastatic Seminoma: Is Modified Template Appropriate? A Retrospective Study

Abstract

Purpose: Several phase 2 trials have investigated the efficacy of retroperitoneal lymph node dissection (RPLND) with a unilateral modified template as the first-line treatment for stage II seminoma. However, the rationale for using modified templates is extrapolated from studies of nonseminomatous germ cell tumor. In this retrospective study, we sought to compare the oncologic outcome of bilateral and unilateral templates and perform a clinical mapping study for metastatic seminoma.

Materials and methods: Patients who presented with pure seminoma at orchiectomy, retroperitoneal only metastasis either at presentation or relapse, and who underwent primary RPLND from 2016 to 2022 at our institution were reviewed. Pathologic and clinical outcomes were compared after stratification based on dissection templates.

Results: The cohort included 104 patients with 36 unilateral and 68 bilateral template dissection. The 2-year recurrence-free survival rate was 80.6% for the unilateral group and 86.8% for the bilateral group. Among the recurrences, 66.7% and 90% were outside of the retroperitoneum in unilateral and bilateral groups, respectively. The most common landing zones of metastatic seminoma are para-aortic for left-sided and interaortocaval for right-sided primary tumors. The microscopic metastasis in the contralateral zones ranges from 6% to 11.1%.

Conclusions: The most common landing zones of seminoma mirror nonseminomatous germ cell tumor. Primary RPLND provides excellent oncologic outcomes for early stage II seminoma. In the early experience in stage II seminoma, we have favored bilateral template dissections. More data are needed to better understand whether bilateral templates should be uniformly performed in pure seminoma.

Keywords: RPLND; lymphatic drainage; metastatic seminoma; modified template; nodal deposition.