High-dose chemotherapy with autologous stem cell transplants in adult primary non-seminoma mediastinal germ-cell tumors. A report from the Cellular Therapy and Immunobiology working party of the EBMT

Background: Primary mediastinal germ-cell tumors (PMGCTs) account for 1%-3% of all germ-cell tumors (GCTs). Non-seminoma have a poorer prognosis compared to their gonadal counterpart and, according to the International Germ Cell Cancer Collaborative Group, they are considered 'poor risk' disease. Medical treatment is the same, with overall survival (OS) being ∼40%, declining to 10%-15% at 3 years in case of lung and non-visceral metastases. Patients failing first-line chemotherapy have a dismal prognosis, with only 5%-10% of cases being cured in the salvage setting. High-dose chemotherapy (HDC) with autologous stem cell transplantation (ASCT) has been successfully used to treat patients with relapsed or refractory gonadal GCTs.

Patients and methods: This retrospective study aimed to investigate the value of HDC with ASCT in the whole population and define primary mediastinal non seminoma germ cell tumor (PMNSGCT) patient subgroups, who were registered in the European Society for Blood and Marrow Transplantation database from January 2000 to January 2018. Sixty-nine adult male patients with PMNSGCT were included. HDC consisted mainly of carboplatin/etoposide doublet, and most patients received HDC as part of a multiple sequential HDC program.

Results: OS was 43.3% at 2 years, and 34.7% at 5 and 10 years for the entire cohort. Analysis of outcomes showed that patients undergoing HDC as upfront therapy had a better progression-free survival (PFS) and OS compared to those treated in subsequent relapses (5-year PFS 51.8% versus 26.8% and 5-year OS 51.3% versus 25.9%). Better remission status before transplantation was predictive of the benefit of HDC. Three treatment-related deaths were recorded.

Conclusions: To our knowledge, this is the most extensive retrospective study of HDC in PMNSGCTs patients and the first to thoroughly investigate potential predictors of benefit from this treatment. HDC with ASCT may well represent a therapeutic option in patients with PMNSGCTs after the first relapse or even as a front-line program.