Phase I and pharmacologic study of irinotecan and etoposide with recombinant human granulocyte colony-stimulating factor support for advanced lung cancer.

Purpose: We conducted a phase I trial of irinotecan (CPT-11), a topoisomerase I inhibitor, combined with etoposide, a topoisomerase II inhibitor, and recombinant human granulocyte colony-stimulating factor (rhG-CSF) support because of the overlapping neutrophil toxicity of both drugs. The aim was to determine the maximum-tolerated dose of CPT-11 combined with a fixed dose of etoposide in patients with advanced lung cancer, as well as the dose-limiting toxicities of this combination.

Patients And Methods: Twenty-five patients with stage III or IV lung cancer, 15 (60%) with prior chemotherapy, were treated at 4-week intervals using CPT-11 (90-minute intravenous infusion on days 1, 8, and 15) plus etoposide (80 mg/m2 intravenously on days 1 to 3). In addition, rhG-CSF (2 micrograms/kg/d) was given from day 4 to day 21, except on the days of CPT-11 administration. The starting dose of CPT-11 was 60 mg/m2, and it was escalated in 10-mg/m2 increments until the maximum-tolerated dose was reached.

Results: The maximum-tolerated dose of CPT-11 was 90 mg/m2, since two of the three patients developed grade 3 to 4 leukopenia or grade 3 to 4 diarrhea during the first cycle of treatment at this dose level. Diarrhea and leukopenia were the dose-limiting toxicities, while thrombocytopenia was only a moderate problem. Elimination of CPT-11 was biphasic, with a mean +/- SD beta half-life of 18.17 +/- 9.09 hours. The mean terminal half-life of 7-ethyl-10-hydroxycamptothecin (SN-38; the major metabolite of CPT-11) was 43.40 +/- 37.84 hours. There was one complete response (5%) and eight partial responses (38%) among 21 assessable patients, for an overall response rate of 43%. The response rates for small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) were 58% (seven of 12 patients) and 22% (two of nine patients), respectively.

Conclusion: The combination of CPT-11 and etoposide with rhG-CSF support seems to be active against lung cancer, especially SCLC, with acceptable toxicity. The recommended dose for phase II studies in previously untreated patients is 80 mg/m2 of CPT-11 (days 1, 8, and 15) and 80 mg/m2 of etoposide (days 1 to 3) plus 2 micrograms/kg of rhG-CSF (days 4 to 21, except when CPT-11 is given). In addition, 70 mg/m2 of CPT-11 appears to be the appropriate dose for previously treated patients receiving this regimen.