GM-CSF, carboplatin, doxorubicin: a phase I study

Dose intensification has the potential to increase the response frequency of chemosensitive tumors to chemotherapy. G-CSF and GM-CSF offer the possibility of dose-intensifying chemotherapy without prohibitive myelosuppression. A phase I study was undertaken to identify the maximum tolerated dose (MTD) of carboplatin that could be administered with a fixed dose of doxorubicin, 60 mg/m², administered every 28 days. Further escalation of the carboplatin dose was then attempted, with the concomitant addition of GM-CSF 10 mg/kg per day on days 1-21. We had 21 patients, 13 with prior therapy, who were eligible. In all, 60 courses of therapy were delivered, all with doxorubicin and with carboplatin doses of 250 mg/m², 325 mg/m² and 400 mg/m². At carboplatin 400 mg/m² and doxorubicin 60 mg/m², thrombocytopenia was dose limiting. The addition of GM-CSF did not allow further escalation. Of the 6 patients treated with carboplatin 400 mg/m², doxorubicin 60 mg/m², and GM-CSF, grade 4 granulocytopenia and thrombocytopenia were seen in 4 and 5 patients, respectively. The severity of thrombocytopenia was related to the calculated carboplatin AUC and also to baseline platelet count and prior therapy. In addition, the interaction of GM-CSF and chemotherapy, especially carboplatin-based, may be more complex than originally anticipated.