THERATEST: A multi-centre observational cohort feasibility study of de-escalation therapies for stage II seminoma.

TPS651 Background: Standard of care (SOC) for stage II seminoma involves primary orchidectomy with combination chemotherapy or external beam radiotherapy, and yield high survival rates but with significant toxicities. Three cycles of Carboplatin AUC10 or robotic retroperitoneal lymph node dissection (rRPLND) with or without adjuvant chemotherapy are promising de-escalation strategies to minimise treatment associated toxicities whilst maintaining oncological outcomes. However, they are not widely adopted due to a lack of comparative data in prospective clinical trials. Therapy De-escalation for Testicular Cancer (THERATEST) aims to assess the feasibility of recruitment for de-escalation strategies for stage II seminoma. Methods: Thirty participants will be recruited over 12 months and treated with either Carboplatin AUC10 or rRPLND with or without adjuvant treatments based on whether the institution offers this treatment as a de-escalation strategy. If participants decline or are not eligible, they will be offered SOC but remain within the study. Both cohorts will be followed up for 2-years. Data collection includes recruitment and retention rates, disease status, surgical outcomes, adverse events and patient-reported outcomes using validated questionnaires which are EORTC QLQ-TC26, EORTC QLQ-C30, the Brief Male Sexual Function Inventory (BMSFI) and additional enquiries on anejaculation. Results: THERATEST has recently commenced recruitment at Barts Health and the Royal Marsden Hospital NHS Trusts. Conclusions: THERATEST is the first endeavour to prospectively evaluate Carboplatin AUC10 and rRPLND as de-escalation strategies for stage II seminoma in a single study. Feasibility of recruitment and retention as well as qualitative and quantitative outcomes data will inform a large-scale multicentre trial. Clinical trial information: ISRCTN61007118 .