Sentence: Our objective was to define the maximum tolerated dose of an escalating dose of ifosfamide in combination with a fixed dose of doxorubicin supported by granulocyte colony-stimulating factor ( Neupogen ) .
Drug combination annotation:
[{'class': 'POS', 'spans': ['ifosfamide', 'doxorubicin'], 'is_context_needed': True}]