Multicenter analysis of high-dose chemotherapy (HDCT) regimens for the treatment of patients (pts) with recurrent germ cell tumors (GCTs).

5039 Background: Although HDCT is an established salvage treatment for pts with GCTs, there is no multi-center comparative analysis of the two most common dosing regimens: 1.) carboplatin 700 mg/m2 and etoposide 750 mg/m2 (CE) given for two cycles, and 2.) carboplatin AUC 7-8 and etoposide 400 mg/m2 given for three cycles, typically after two cycles of paclitaxel 200 mg/m2 and 2000 mg/m2x (TICE). To address this gap, we pooled data from four high-volume referral centers to evaluate the clinical efficacy of HDCT approaches. Methods: Demographic and clinical characteristics were retrospectively abstracted from electronic medical charts. Adult pts who received HDCT for recurrent GCT from 1/1/2010 to 1/1/2023 and received either CE or TICE were included. Differences among groups were tested using the Fisher's exact and the Wilcoxon rank-sum tests for qualitative and quantitative variables, respectively. Relapse-free survival (RFS) and overall survival (OS) were estimated and compared using the Kaplan-Meier method and log-rank test. All statistical analyses were conducted in R Statistical Software, version 4.3.1. Results: Seventy-two pts were identified across four institutions, of whom 46 received CE (64%) and 26 received TICE (36%). Most CE pts were treated at UCSF (39%) or UCLA (22%); TICE was predominantly given at COH (46%) or UCSF (46%). Median age at diagnosis was 30 (range, 18-58), a majority were Hispanic (51%), and most pts had a non-seminomatous GCT (79%). Ethnicity and tumor histology were similar between all two cohorts (P=NS for both). Most pts had Stage IIIC disease at diagnosis (44%) and most received HDCT in the 3 rd line setting (71%). Tumor marker normalization prior to HDCT was more prevalent among CE (35%) than TICE (15%). Most pts who received CE (89%) and TICE (77%) completed their planned two and three cycles of HDCT, respectively. With a median follow-up of 54.0 months from the date of the last transplant, no difference was observed in the median RFS between TICE vs CE (10.2 vs 4.5 months, HR of 0.87, 95% CI 0.51, 1.49, P=0.610. We observed a trend toward improved median OS between TICE vs CE (56.5 vs 17.9 months, HR 0.54, 95% CI 0.29, 1.01, P=0.057). There was no difference between the rates of post-transplant relapse among pts who received HDCT in the 2 nd line vs 3 rd line (76.9% vs 61.7%, P=0.51). Conclusions: In the first multicenter comparative analysis of contemporary HDCT regimens, there was no difference in RFS between CE and TICE. However, we observed a trend toward improved survival among pts who received TICE. Additionally, we detected no difference in the rates of post-transplant relapse among pts treated in the 2 nd line versus the 3 rd line, supporting the application of HDCT in either setting. These findings represent the first of an ongoing regional collaboration that aims to leverage real-world data to improve clinical outcomes for pts with recurrent GCTs.