Background: Selected patients with advanced germ cell tumors have a poor prognosis. These include patients with brain, bone or liver metastases, very elevated tumor markers or primary mediastinal tumor. High-dose chemotherapy (HDCT) with autologous stem cell support is recommended in the Swedish and Norwegian Testicular Cancer Group (SWENOTECA) guidelines in selected poor risk patients with poor response to/relapse after intense primary treatment. From the year 2011, the HDCT-regimen consisted of two cycles of carboplatin and etoposide. Our aim of this study was to evaluate survival and toxicity in patients treated with HDCT within the population-based SWENOTECA cancer care program in 2011-2021. Methods: All patients treated with HDCT according to guidelines in Sweden and Norway between 2011-2021 were included, in total 80 patients (76 non-seminoma and 4 seminoma). This reflected approximately 3% of all non-seminoma patients. HDCT was administered in three different clinical situations: delayed tumor marker decline during primary or intensified primary treatment (n=26), progressive disease during primary treatment (n=29) (defined as progressive disease within <3 months from last cycle of chemotherapy), or relapse with poor prognosis (n=25). The overall survival (OS) and failure-free survival (FFS) were calculated, and the toxicity was described. Results: The 5-year overall survival (OS) and failure free survival (FFS) after HDCT was 55% and 43% respectively. HDCT due to delayed tumor marker decline had a more favorable outcome, 5-year OS of 75% and 5-year FFS of 53%. HDCT due to relapse resulted in a 5-year OS of 61% and 5-year FFS of 58%. Patients treated with HDCT due to progressive disease during primary treatment had a markedly less favorable 5-year OS of 29% and 5-year FFS of 18%. Four patients (5%) died due to treatment. The most common treatment-related grade 3-4 toxicities were infections (n=69, 86%). Conclusions: In this population-based study, we have shown that HDCT for patients with advanced germ cell cancer according to the SWENOTECA cancer care program is achievable and leads to favorable OS and FFS rates. Furthermore, even though patients that receive HDCT due to progressive disease have a relatively poor outcome, 20-30% of patients do achieve long-term survival.

*Mortality due to HDCT-treatment 4/80 (5%).