Inclusion Criteria:  Patients with TC who will start or already started treatment with (B)EP Age of at least 18 years Patients from whom it is possible to collect blood samples Patients who are able and willing to give written informed consent prior to screening  Exclusion Criteria:  Patients who are co-treated with drugs that could interfere with the metabolism of etoposide (including drugs classified as a weak, moderate or strong CYP3A4 inhibitor OR weak, moderate and strong inducers of CYP3A4 according to the table based on the Flockhart table (Appendix 1) less than 30 days prior to study or during the study. Creatininclearance <40 ml/min Severe liver dysfunction (bilirubin>ULN)