Evaluation of an intermittent schedule of dibromodulcitol in breast cancer

Dibromodulcitol was administered orally on Days 1-10 every 3-4 weeks to 29 patients with metastatic breast carcinoma refractory to previous combination chemotherapy. Initial doses between 70 and 280 mg/m2/day were utilized. The dose was escalated as tolerated in subsequent cycles in individual patients. Hematosuppression was dose-limiting. At doses of greater than 200 mg/m2/day leukopenia (greater than 1000 cells/mm3) and thrombocytopenia (greater than 25,000 platelets/mm3) occurred in one of 28 cycles and two of 27 cycles respectively. In contrast, at doses of less than or equal to 200 mg/m2/day leukopenia and thrombocytopenia occurred in four of 18 cycles and five of 18 cycles respectively. Recovery of leukocytes (less than 4000 cells/mm3) and platelets (less than 100,000 platelets/mm3) by Day 29 after the start of therapy was also delayed at higher doses. Responses were observed in three of 29 evaluable patients and subjective improvement of osseous disease in one additional patient. A dose of 180 mg/m2/day X 10 Every 28 days is recommended in previously treated patients to avoid severe hematologic side effects.