Cyclophosphamide, ara-C and topotecan (CAT) for patients with refractory or relapsed acute leukemia

Topotecan is a topoisomerase I inhibitor with significant activity in patients with myelodysplastic syndrome and chronic myelomonocytic leukemia. Pre-clinical data suggest a synergistic activity with DNA damaging agents such as cyclophosphamide, where topotecan might prevent the repair of cyclophosphamide-induced DNA damage. We thus designed a combination including cyclophosphamide 500 mg/m² every 12 hours given on days 1 to 3; topotecan 1.25 mg/m²/day by continuous infusion on days 2 to 6, and cytosine arabinoside (ara-C) 2 g/m² over 4 hours daily for 5 days on days 2 to 6 (CAT). Sixty six (63 evaluable) patients were treated. Fifty two patients had refractory (n = 12) or relapsed (n = 40) acute myelogenous leukemia (AML), and eleven had acute lymphocytic leukemia (ALL) (refractory n = 3, relapsed n = 8); their median age was 57 years (range, 18 to 79 years). Eleven patients (17%) achieved a complete remission (CR), and two patients (3%) had a hematologic improvement (HI; met all criteria for CR except for platelets < 100 x 10⁹/L), for an overall response rate of 20%. Responses occurred in 12 of 52 AML patients (23%), including 10 CR (19%) and 2 HI (4%), and in 1 of 11 patients with ALL (9%). Myelosuppression was universal; there were 23 episodes of pneumonia or sepsis and 18 episodes of fever of unknown origin complicating 74 courses of CAT. Non-hematologic toxicity was mostly gastrointestinal, including nausea, vomiting, diarrhea and mucositis, but was severe in only 8%. In summary, the CAT regimen is well tolerated and has significant anti-leukemia activity which warrants further investigation.