His main research is focused on ‘tailored therapy’ of systemic anti-cancer agents like chemotherapy, anti-hormonal therapy, tyrosine kinase inhibitors, and immunotherapy.
To implement therapeutic drug monitoring (TDM) in daily oncological clinical practice is one of his major goals for the coming years.

He published over 300 peer reviewed papers and book chapters. In addition, he is the chair of the Dutch Pharmacology Oncology Group (www.dpog.nl); a nationwide collaboration to individualize the dosing of (oral) anti-cancer drugs.