High-dose chemotherapy (HDCT) and peripheral-blood stem-cell transplant (PBSCT) for relapsed seminoma: A single-center cohort.

e17013 Background: The optimal salvage therapy for patients with relapsed seminoma remains unsettled. We evaluated clinical characteristics, outcomes, and toxicity in patients with relapsed seminoma treated with HDCT and PBSCT as second-line or subsequent therapy. Methods: We performed a retrospective analysis of consecutive patients with relapsed seminoma who received salvage HDCT and PBSCT at Indiana University between 2001-2026. HDCT consisted of two planned tandem cycles of high dose carboplatin and etoposide. Patient, disease, and treatment characteristics were abstracted from institutional records. Primary endpoints included progression-free survival (PFS) and overall survival (OS) after HDCT estimated with the Kaplan-Meier method. Secondary endpoints included the number of cycles of HDCT received, dose modifications, and grade ≥3 toxicities. Results: A total of 147 patients were included with a median age of 38 years (range 20-70) and median follow-up of 3.5 years from date of start of HDCT (range 0.0-19.1). Primary tumor sites were testicular (91.8%), retroperitoneal (6.8%), and mediastinal (1.4%). Metastatic sites included lungs in 13.6%, non-pulmonary visceral metastases (NPVM) in 21.1% (bone 12.9%, liver 6.1%, brain 4.1%), and lymph nodes in all 147 patients. HDCT was administered as second-line therapy in 81.0% and as ≥third-line therapy in 19.0%. 9.5% of patients had platinum refractory disease defined as progression within 4 weeks of first-line cisplatin-based chemotherapy. Both planned tandem HDCT cycles were completed in 91.2% of patients and dose reductions occurred in 10.9%. Grade ≥3 toxicity occurred in 57.8%, most commonly gastrointestinal (42.7%) and infectious (27.4%). The estimated 2-year PFS was 89.4% (95% CI 82.7%-93.6%) and 5-year PFS was 86.3% (77.9%-91.7%). The estimated 2-year OS was 93.1% (87.1%-96.4%) and 5-year OS was 87.6% (78.9%-92.3%). Five-year PFS for HDCT given as 2nd line compared to ≥3rd line was 90.2% (82.3%-94.6%) vs 70.8% (43.3%-86.8%). Five-year OS for HDCT given as 2nd line compared to ≥3rd line was 93.0% (85.7%-97.4%) vs 67.3% (39.1%-94.6%). Death occurred in 11.6%, with a median time from HDCT to death of 13 months (range 0-191). Treatment related death occurred in 2 patients (1.4%). At last follow-up, 85.7% of patients had no evidence of disease. Conclusions: HDCT + PBSCT is an effective salvage therapy for patients with relapsed seminoma. HDCT as initial salvage chemotherapy in seminoma provided unprecedented PFS and OS and remained effective as ≥3rd line therapy. Given the very high cure rates observed with HDCT alone, our experience suggests that routine use of standard-dose salvage chemotherapy prior to HDCT may not be necessary in appropriately selected patients.