A quinonemethide triterpenoid is administered to subjects with multidrug-resistant cancer, in particular a cancer with enhanced expression and/or functional activity of ABC transporter proteins such as P-glycoprotein and/or an apoptosis-deficient, in particular p53-, Bax- or Bak-deficient, cancer, i.e. specific subgroups of subjects with cancer. The quinonemethide triterpenoid is suitable to treat cancer allowing for an accumulation of cytotoxic or therapeutic compounds in the cells while having exceptionally increased cytotoxic activity towards the multidrug-resistant cancer cells and while allowing for an increased activity of chemotherapeutic compounds. Methods for specifically targeting cancer cells with multidrug-resistance and methods for potentiating the activity of a chemotherapeutic compound in those cancer cells are also disclosed. A kit including a quinonemethide triterpenoid and a chemotherapeutic compound is also provided.