A phase I-II study of cyclophosphamide, thiotepa, and carboplatin with autologous bone marrow transplantation in solid tumor patients

The principles of dose-response and combination chemotherapy were basic to the design of the initial curative standard-dose treatment regimens for leukemias, lymphomas, and testis cancer. Agents were selected with different dose-limiting toxicities, resulting in subadditive toxicity in combination. A fourth principle in the design of curative regimens was to combine agents with different mechanisms of action to avoid cross-resistance. Based on these principles, combinations of the highest tolerated doses of active noncross-resistant agents are required to decrease the emergence of drug resistance and achieve optimum cytotoxicity. Hematopoietic stem-cell support provides a mechanism for significantly increasing the doses of active agents, a strategy that has resulted in the cure of 10% to 50% of selected patients with lymphoma who could not be cured with standard-dose therapy. The lack of sufficiently effective cytoreductive conditioning regimens remains the major impediment to improving the high-dose therapy of patients with solid tumors. In this study, 27 patients with solid tumors were treated with a combination of cyclophosphamide, thiotepa, and carboplatin (CTCb) in a phase I-II study. Severe mucositis and neurotoxicity were dose-limiting. The maximum-tolerated dose (MTD) of the combination was 6.0 g/m2 of cyclophosphamide, 500 mg/m2 of thiotepa, and 800 mg/m2 of carboplatin. There were two deaths (7%) of sepsis, and an overall response rate of 72% in refractory tumors (81% in breast cancer). CTCb is a combination with low morbidity and high cytoreductive efficacy designed to exploit the principles of curative cancer chemotherapy.