Clinical Outcomes of De Novo Versus Relapsed Early Metastatic Testicular Seminoma Treated With Contemporary Radiation Therapy.

Purpose: Chemotherapy (CHT) or radiation therapy (RT) are first-line treatments for clinical stage II (CS-II) testicular seminoma. Historically, clinical stage I (CS-I) seminoma was also treated with CHT or RT, but in the past 2 decades practice has shifted toward active surveillance for CS-I with RT or CHT reserved for patients with progression to CS-II. Limited data exist on contemporary RT techniques and patient stratification (ie, de novo [CS-II at orchiectomy] vs relapsed [CS-II diagnosed during surveillance after orchiectomy for CS-I]). We investigated outcomes in CS-II patients treated with RT in the modern era across 2 institutions.

Methods And Materials: A retrospective review identified 73 patients treated with RT for CS-II A or B seminoma between 2001 and 2022. Recurrence-free survival (RFS) was calculated by the Kaplan-Meier method and univariate analyses were performed with log-rank or Cox proportional hazard regression. Recurrence was defined as biopsy-proven metastatic seminoma after RT completion. Second malignancies were defined as a biopsy-proven malignancy originating in the prior RT field.

Results: Thirty-eight (52%) patients presented with de novo CS-II and 35 (48%) patients had relapsed CS-II. Median follow-up was 4.8 years (IQR: 2.3-8.1). Five-year RFS was 82% overall (92% in relapsed patients and 73% in de novo patients). Relapsed CS-II disease had lower recurrence rates after RT compared with de novo CS-II disease. All recurrences occurred outside the prior RT field and were salvaged. Disease-specific survival was 100%. Two second malignancies occurred (prostate, colorectal cancer at 67 months and 119 months post-RT, respectively).

Conclusions: In patients with CS-II seminoma treated with modern RT, there were no in-field recurrences. Presentation with de novo CS-II is associated with out-of-field recurrence. Subject to further larger-scale validation, our results suggest that compared with CS-II at time of relapse, de novo CS-II may portend more aggressive or micrometastatic disease beyond the retroperitoneum, raising the possibility of benefit from CHT after radiation.