Phase I study of repeated cycles of high-dose cyclophosphamide, etoposide, and cisplatin administered without bone marrow transplantation Forty-two patients with advanced malignancy judged unlikely to respond to standard treatment received high-dose combination chemotherapy with cyclophosphamide, etoposide, and cisplatin in a phase I trial. Twenty-two of these patients who had at least a partial response (PR) to the first cycle of therapy received a second cycle, and eight patients received three or more cycles of therapy. Bone marrow replacement was not used. The maximum-tolerated doses (MTDs) were cyclophosphamide 2.5 g/m2 on days 1 and 2; etoposide 500 mg/m2 on days 1, 2, and 3; and cisplatin 50 mg/m2 on days 1, 2, and 3. Hematologic toxicity was not dose-limiting by study design. Recovery to an absolute granulocyte count above 100/microL occurred at a median of 9 days from onset (range, 3 to 23 days) at the MTD. Recovery was delayed after the third cycle. Only one patient on his third cycle failed to recover peripheral blood counts and died of sepsis an day 43. Hematologic toxicity was not dose-dependent. Nonhematologic toxicities included emesis, fatigue, alopecia, diarrhea, and anorexia and were generally well tolerated. The dose-limiting toxicities were fatal pulmonary or cardiac toxicities in five of nine patients treated at the highest dose level. Patients likely to do well can be selected by tumor type, response to prior therapy, and performance status. Nine of 36 assessable patients had a complete response (CR) and 13 a PR for a response rate of 61%. Five patients (12%) remain alive and free of disease at 15 to 32 months. Repeated cycles of dose-intensive combination therapy can produce long-term disease-free remissions in patients with refractory tumor types. The toxicity of the regimen is acceptable if patients are carefully selected. 