GAMMA: Results from a phase II study for relapsed germ cell tumors using an oxaliplatin-based treatment regimen.

Abstract

417 Background: Following relapse from first line chemotherapy, 30-60% of patients with germ cell tumors (GCTs) can be salvaged with further chemotherapy. Oxaliplatin-based therapies may offer reduced toxicity. Methods: Eligible patients with GCTs who progressed following cisplatin-based chemotherapy were recruited into this single-arm, phase II clinical trial (NCT01782339). Participants were recruited from six centers and received four 21-day cycles of: Actinomycin D 1mg/m2, high dose Methotrexate 5-8g/m2 day 1, Paclitaxel 80mg/m2 days 1, 8 and 15, Oxaliplatin 85mg/m2 days 4 and 8 with Pegfilgrastim support. Participants underwent an FDG-PET scan at baseline, prior to cycle 2 and on completion of treatment. The primary endpoint was objective response rate (ORR). Secondary endpoints were progression-free survival (PFS), overall survival (OS) and toxicity. Results: 44 patients received at least one dose of the study medication between November 2012 and February 2020. In this full analysis set (FAS) population, the median age was 38 (range 20-57), with 9 (20%) with seminoma, 23 (52%) non-seminoma and 12 (27%) of other histology. 31 (70%) patients had at least intermediate risk disease by IPFSG risk group criteria (n = 16, 36% intermediate risk, n = 6, 14% high risk, n = 9, 20% very high risk). 39 patients received 2 or more cycles of the treatment regimen and were deemed part of the subgroup of patients in the evaluable population. The ORR of the FAS population was 52.3% and 59.0% in the evaluable population. The metabolic response rate (MRR) was 52.3% in the FAS population and 59.0% in the evaluable population. The median radiological PFS in the FAS population was 17.0 months (95% CI, 5.7 months- not reached, NR) with a radiological PFS rate at two years of 38.7% (95% CI, 22.3%-54.9%). The median combined radiological or tumour marker PFS in the FAS population was 8.3 months (95% CI, 2.6 months-17.4 months) with a combined radiological or tumour marker PFS rate at two years of 28.9% (95% CI, 16.0%-43.1%). At a median follow-up of 26.8 months, the median OS in the FAS population was not reached (95% confidence interval [CI], 17.0 months-NR) with an OS rate at two years of 62.5% (95% CI, 46.1%-75.2%). Toxicity data and correlation between early metabolic response and outcomes will be presented at the meeting. Conclusions: The GAMMA chemotherapy regimen has demonstrated encouraging anti-tumor activity in relapsed GCT, despite recruiting a cohort of patients with relatively unfavorable outcomes. Clinical trial information: NCT01782339.