A phase I dose escalation study of high-dose thiotepa, melphalan and carboplatin (TMCb) followed by autologous peripheral blood stem cell transplantation (PBSCT) in patients with solid tumors and hematologic malignancies

The purpose of this study was to determine the maximum tolerated dose of carboplatin administered with 500 mg/m² thiotepa and 100 mg/m² melphalan followed by autologous peripheral blood stem cell (PBSC) infusion in patients with refractory malignancies. Twenty-eight patients with refractory malignancies received high-dose thiotepa (500 mg/m², melphalan (100 mg/m2) and escalating doses of carboplatin 900-1500 mg/m²) followed by infusion of cryopreserved autologous PBSCs. The maximum tolerated doses were determined to be 500 mg/m² thiotepa, 100 mg/m2 melphalan and 1350 mg/m2 carboplatin. Two consecutive patients receiving 1500 mg/m² carboplatin experienced grade 3 mucositis and colitis. Ten patients were enrolled at the maximum tolerated dose and none had grade 3-4 regimen-related toxicity and mortality. All patients at this level experienced grade 1-2 mucositis, 90% grade 1-2 gastrointestinal toxicity, 30% grade 1-2 cardiac and renal toxicity, and 10% experienced grade 1 hepatic toxicity. The median time to achieve a granulocyte count of 0.5 x 10⁹/l was 9 days (range 7-12 days) and platelet count of 20 x 10⁹/l was 10 days (range 7-15 days). Of eight patients with stage IV refractory breast cancer, even were evaluable for response, one patient on day 75 will be evaluated soon. Five of seven (71.5%) evaluable patients achieved a complete remission (CR) and two had no response. Of seven patients with non-Hodgkin's lymphoma (n = 4) or Hodgkin's disease (n = 3), five achieved a CR (71.5%). Thiotepa, melphalan and carboplatin can be administered in high doses with tolerable mucositis as the major side-effect. This combination has significant activity in patients with breast cancer, and phase II studies in patients with breast cancer and other chemotherapy-sensitive malignancies are warranted.