High-dose infusional doxorubicin and cyclophosphamide: A feasibility study of tandem high-dose chemotherapy cycles without stem cell support

The purpose of this study was to determine the maximally tolerated dose of doxorubicin administered during two cycles of intensive chemotherapy with cyclophosphamide and doxorubicin without stem cell support in patients with advanced cancer and to assess the cumulative cardiac toxicity of the regimen by noninvasive radionuclide imaging and by pre- and postchemotherapy endomyocardial biopsies. Thirty-eight patients (thirty-six with high risk or metastatic breast cancer) were treated in a dose-escalation trial using a fixed dose of i.v. cyclophosphamide (4.2 g/m²) administered over 2 h on day 5 and escalating doses of doxorubicin (50-175 mg/m²) given as a 96-h continuous i.v. infusion on days 1-4, using Filgrastim (granulocyte colony- stimulating factor) for hematological support beginning on day 6. All patients underwent pretreatment, and 28 patients underwent postchemotherapy endomyocardial biopsies. Twenty-nine of 38 patients received two cycles of treatment (median number of days between cycles, 44; range, 34-62). Twenty- one patients had received doxorubicin previously at cumulative dose levels ≤150 mg/m²; all patients had pretreatment endomyocardial biopsy scores less than 1. One patient treated at the highest dose level of doxorubicin (175 mg/m²) developed symptoms of mild congestive heart failure following two cycles of chemotherapy. Pre- and posttreatment radionuclide ejection fractions were 65 and 45%, respectively; this patient had a posttreatment endomyocardial biopsy score of 1 (damage to <5% of myocytes). One additional patient at this dose level had an asymptomatic biopsy score of 1, with a decrease in ejection fraction from 62 to 43%; this recovered to 58% 5 months after completion of chemotherapy. Six additional patients treated at lower dose levels had abnormal posttreatment endomyocardial biopsies without abnormal posttreatment ejection fractions. Nine patients received only one cycle of chemotherapy: five patients due to decreased cardiac ejection fraction following cycle 1 (two of these patients had normal endomyocardial biopsies, and two patients had biopsy scores of 1); one patient secondary to tumor progression following cycle one; one patient due to persistently detectable Clostridium difficile toxin in the stool; one patient refused cycle two; and one patient died following cycle one of complications related to sepsis. A single patient experienced a grand mal seizure associated with orthostatic hypotension, which was considered the dose-limiting toxicity. The median duration (over two cycles) of granulocytopenia (absolute granulocyte count <500/μl) at the maximally tolerated dose level of 150 mg/m² was 8.5 days (range, 5-13 days), and the median duration of thrombocytopenia (platelets <20,000/μl) was 2.5 days (range, 0-9 days). The median duration of hospitalization including chemotherapy administration was 23 days (range, 19-36 days). Other toxicities included stomatitis, fever, diarrhea, and emesis. One patient developed acute leukemia 54 months posttreatment. We conclude that two courses of high-dose cyclophosphamide and doxorubicin using granulocyte colony-stimulating factor are feasible and safe with tolerable myocardial toxicity as evidenced by serial endomyocardial biopsies. The dose- limiting toxicity encountered was a grand mal seizure. The recommended Phase II dose is doxorubicin 150 mg/m² administered as a 96-h infusion on days 1- 4, with cyclophosphamide 4.2 g/m² on day 5 and G-CSF 5 μg/kg/day started on day 6 and administered until the total WBC is above 10,000/μl for three consecutive days.