Phase I and pharmacologic study of high doses of the topoisomerase I inhibitor topotecan with granulocyte colony-stimulating factor in patients with solid tumors.
OBJECTIVE
To evaluate the feasibility of escalating doses of the topoisomerase I (topo I) inhibitor topotecan (TPT) with granulocyte colony-stimulating factor (G-CSF) in minimally pretreated adults with solid tumors and to study whether G-CSF scheduling variably affects the ability to escalate TPT doses.


METHODS
Thirty-six patients received 121 courses of TPT as a 30-minute infusion daily for 5 days every 3 weeks at doses that ranged from 2.0 to 4.2 mg/m2/d. G-CSF 5 microg/kg/d subcutaneously (SC) was initiated concurrently with TPT (starting on day 1). Because the concurrent administration of TPT and G-CSF resulted in severe myelosuppression at the lowest TPT dose level, an alternate posttreatment G-CSF schedule in which G-CSF dosing began after TPT (starting on day 6) was subsequently evaluated. Plasma sampling was performed to characterize the pharmacologic behavior of high-dose TPT and to determine whether G-CSF altered the pharmacokinetic profile of TPT.


RESULTS
Severe myelosuppression precluded the administration of TPT at the first dose, 2.0 mg/m2/d, with G-CSF on the concurrent schedule. However, dose escalation of TPT with G-CSF on a posttreatment schedule proceeded to 4.2 mg/m2/d. The dose-limiting toxicities (DLTs) were thrombocytopenia and neutropenia. One partial response was noted in a patient with colorectal carcinoma refractory to fluoropyrimidines. Pharmacokinetics were linear within the dosing range of 2.0 to 3.5 mg/m2/d, but TPT clearance was lower at the 4.2-mg/m2/d dose level. At 3.5 mg/m2/d, which is the maximum-tolerated dose (MTD) and recommended dose for subsequent-phase studies of TPT with G-CSF, the area under the concentration-versus-time curves (AUCs) for total TPT and lactone averaged 2.2- and 2.3-fold higher, respectively, than the AUCs achieved at the lowest TPT dose, 2.0 mg/m2/d. The pharmacologic behavior of high-dose TPT was not significantly altered by the scheduling of G-CSF.


CONCLUSIONS
G-CSF administered after 5 daily 30-minute infusions of TPT permits a 2.3-fold dose escalation of TPT above the MTD in solid-tumor patients, whereas concurrent therapy with G-CSF and TPT results in severe myelosuppression.
Rowinsky
E K
EK
Division of Pharmacology, The Johns Hopkins Oncology Center, Baltimore, MD, USA.
Grochow
L B
LB
Sartorius
S E
SE
Bowling
M K
MK
Kaufmann
S H
SH
Peereboom
D
D
Donehower
R C
RC
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D002166:Camptothecin / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use; D004334:Drug Administration Schedule; D005240:Feasibility Studies; D005260:Female; D016179:Granulocyte Colony-Stimulating Factor / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy*; D059004:Topoisomerase I Inhibitors; D019772:Topotecan; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D059004:Topoisomerase I Inhibitors; D016179:Granulocyte Colony-Stimulating Factor; D019772:Topotecan; D002166:Camptothecin