Testicular cancer is the most common cancer in men between the ages of 15 and 45, although it accounts for only 1-2% of all tumors in men. Ninety-five percent of testicular tumors are germ cell tumors (GCTs), which are divided into two types: seminomas and non-seminomas. The treatment of patients usually begins with a combination of surgery and chemotherapy. First-line chemotherapy with cisplatin cures approximately 80% of patients with metastatic germ cell tumors, but 20% to 30% will relapse after first-line chemotherapy. This minority of patients with relapsed metastatic GCT are more difficult to treat. Second-line chemotherapy can lead to a cure, but the optimal approach for this has not been established. International guidelines recommend either standard-dose chemotherapy (SDCT) programs combining cisplatin and ifosfamide with either paclitaxel or vinblastine or high-dose chemotherapy (HDCT) with autologous stem cell transplant (ASCT). HDCT should be employed in third or later line chemotherapy, if not already used earlier. The most commonly used HDCT regimen is high-dose carboplatin and etoposide followed by ASCT. This thesis reports the outcomes of HDCT in 15 patients with GCT treated at Ghent University Hospital between 2009 and 2022. We compared these results with findings from 21 other studies evaluating HDCT approaches, combining insights from the medical literature with a detailed analysis of our own patient group. Patients received either the CarboPEC regimen (carboplatin, etoposide and cyclophosphamide) or the CarboPE regimen (carboplatin and etoposide). Seven patients received one cycle and 8 patients received two cycles. The median and mean follow-up time since HDCT were 50 and 71.5 months, respectively. After three years, 9 patients (60%) were still alive, and 7 patients (46.7%) had no signs of disease progression. Due to variability between studies, a superior HDCT regimen could not be identified. The results of 15 patients at the University Hospital of Ghent are largely consistent with international survival outcomes. Therefore, there seems no need to adjust the existing high-dose chemotherapy regimen for advanced relapsed germ cell tumors at this hospital, although every patient who cannot be cured remains one too many. For future research, there is a need for a study where people are randomly assigned to different treatment groups to compare HDCT with SDCT in the second-line setting. Another study should also compare different HDCT treatment plans and determine the optimal number of HDCT cycles for patients. This thesis contributes to the medical community and patient care. The patients impacted are predominantly young men, for whom many quality-adjusted life years depend on receiving the best possible salvage therapy.