Validation of new prognostic factors for relapse in patients with clinical stage I seminoma.

625 Background: Patients with clinical stage I (cSI) seminomatous testicular germ cell tumors (GCT) have a relapse risk of 5 - 30% under surveillance after orchiectomy, depending on tumor size and rete testis infiltration. Recently, two studies introduced new prognostic risk models to improve clinical decision-making: the Danish Testicular Cancer database (DaTeCa) and an Individual Patient Data Analysis by the European Association of Urology (EAU) Testicular Cancer Guidelines Panel and Guidelines Office. This study aimed to validate these new prognostic risk models in an independent cohort of cSI seminoma patients. Methods: We included patients with unilateral cSI seminoma (retroperitoneal lymph nodes <10 mm in short-axis diameter), normalized serum tumor markers post-orchiectomy (β-human chorionic gonadotropin (β-hCG) and lactate dehydrogenase (LDH)), and no adjuvant therapy. All patients had at least 12 months of follow-up. Cox regression analysis was applied to evaluate the proposed prognostic factors and relapse probabilities were estimated using the Kaplan-Meier method. Results: Among 139 patients, 25 (18%) relapsed within a median follow-up of 37 months (CI 47.9–63.1). In multivariate analysis, only rete testis infiltration was confirmed as an independent predictor of relapse (p=0.039). The other prognostic factors of DaTeCa (lymphovascular invasion, elevated pre-orchiectomy β-hCG and LDH) and EAU (tumor size and lymphovascular invasion) could not be confirmed. The 5-year relapse risk according to DaTeCa risk groups was consistent with our cohort (no risk factors: 4% vs. 6%; all four risk factors: 67% vs. 62%). Similarly, the EAU classification showed comparable 5-year relapse risks for low (13% vs. 8%) and intermediate (22% vs. 20%) groups. However, the high-risk group showed a greater discrepancy (67% vs. 44%), although our study included only a limited number of high-risk patients (n=6, 4.3%). Conclusions: The risk classification models from DaTeCa and EAU demonstrated good overall reproducibility in our cohort. These models may aid in identifying seminoma patients at high-risk for relapse who might be candidates for adjuvant therapy. However, the proposed prognostic factors were mainly not independently confirmed in the multivariate analysis in our study cohort.