Etoposide dosing challenges in a testicular cancer patient with hepatic impairment and drug-drug interactions–a case report

Purpose Etoposide, together with cisplatin, is a cornerstone in the treatment of metastatic testicular cancer, but dosing can be challenging in patients with organ dysfunction and/or polypharmacy. We report a patient with cystic fibrosis, liver cirrhosis and preexisting pancytopenia grade 1, requiring multiple concomitant medications inhibiting CYP3A4 and P-gp, who presented with metastatic seminoma. Method and results Due to potential drug-drug interactions and liver cirrhosis, the initial etoposide dose was reduced to 50% of standard. Monitoring of etoposide plasma concentrations showed that total exposure was not enhanced. The subsequent dose was increased to 100% and further adjusted based on tolerability. After a dose reduction from cycle 2 due to pancytopenia grade 4, the patient successfully completed the chemotherapy regimen and had a complete response on first evaluation. Conclusion This case shows that monitoring of etoposide plasma concentrations can be beneficial in complex clinical scenarios involving organ dysfunction and/or potential drug-drug interactions. This is especially important in curative treatment to avoid under dosing. Patient summary This case report highlights the challenges of dosing etoposide in a patient with cystic fibrosis and liver cirrhosis who is taking multiple drugs that may interact with etoposide. The patient should be monitored closely on how the treatment is tolerated and the dose should be adjusted accordingly.