622 Background: Clinical stage I (CSI) testicular germ cell neoplasms (tGCN) represent the most frequent disease presentation and are highly curable. While active surveillance (AS) is increasingly favored as initial management, practice heterogeneity persists. The SWOG/CCTG S1823/GCC-001 trial is a prospective, non-interventional cohort study evaluating microRNA 371a-3p as a diagnostic biomarker in germ cell tumors. We hereby present a pre-planned secondary analysis of this dataset to characterize real-world treatment patterns and baseline characteristics of CSI tGCN across North America. Methods: We included patients from S1823 with pathologically confirmed CSI tGCN (seminoma or nonseminoma). Patients with metastatic disease, marker-positive status post-orchiectomy, or recurrent disease were excluded. Demographic, pathologic, and intended management data were extracted from case report forms and institutional source documents, as intended per pre-planned secondary use of data provisions. Results: Among 706 patients with CSI tGCN (428 seminoma, 278 nonseminoma), median age was higher in seminoma (38.7±10.7 years) than nonseminoma (32.4±9.4). There was a high prevalence of overweight or obese habitus (36.0% and 32.2%, respectively). AS was the most commonly selected management strategy: 92.1% in seminoma and 79.9% in nonseminoma. Adjuvant chemotherapy was used more often in nonseminoma (16.2%) than seminoma (6.3%), typically one cycle of BEP or carboplatin respectively. Radiation was nearly absent (<1%). Across both histology groups, adjuvant chemotherapy was prescribed more frequently in U.S. centers than in Canada (seminoma: 8.4% vs 0.8%; nonseminoma: 19.2% vs 5.1%). Conclusions: AS is the predominant management strategy for CSI tGCN across North America, with limited use of adjuvant therapy. However, treatment patterns vary by histology and geography, with notably higher adjuvant chemotherapy use in the U.S. compared to Canada. These findings illustrate evolving practices and highlight the utility of large prospective registries to assess real-world care. Full S1823 trial analysis may further inform risk-adapted strategies in CSI tGCN. Clinical characteristics and management recommendations for CSI seminoma and nonseminoma patients enrolled on S1823. Clinical Characteristics Histology Race/Ethnicity White/Non-White/Hispanic pT stage pT1/pT2 Institution LAPS/NCOPR/Other Age (mean) BMI Sem 428 (60.6%)Non-sem 278 (39.4%) 79.2%/20.8%/16.1% 446 (63.2%)/ 250 (35.4%) 18%/38%/42% 36.2 Underwt. 1.1%Normal 30.4%Over Wt. 36.0%Obese 32.1% Planned Management Active surveillance Chemo Radiation Surgery Yes 616 (87.3%) BEP X1 41 (5.8%)Carbo X1 19 (2.7%)Carbo X2 6 (0.8%) Yes 2 (0.3%) Yes 18 (2.5%) Sem= seminoma; Non-sem= nonseminoma; BMI= body mass index; BEP= Bleomycin, Etoposide, Cisplatin; Carbo= Carboplatin.
Coulombe et al. (Sun,) studied this question.