A phase I and pharmacokinetic study of fixed-dose selenomethionine and irinotecan in solid tumors.
OBJECTIVE
We conducted a phase I study to determine the maximum tolerated dose (MTD) of irinotecan with fixed, nontoxic high dose of selenomethionine.


METHODS
Selenomethionine was given orally as a single daily dose containing 2,200 mug of elemental selenium (Se) starting 1 week before the first dose of irinotecan. Irinotecan was given i.v. once weekly x 4 every 6 weeks (one cycle). The starting dose of irinotecan was 125 mg/m(2)/wk. Escalation occurred in cohorts of three patients until the MTD was defined. Pharmacokinetic studies were done for selenium and irinotecan and its metabolites.


RESULTS
Three of four evaluable patients at dose level 2 of irinotecan (160 mg/m(2)/wk) had a dose-limiting diarrhea. None of the six evaluable patients at dose level 1 (125 mg/m(2)/wk irinotecan) had a dose-limiting toxicity. One patient with history of irinotecan-refractory colon cancer achieved a partial response. The long half-life of selenium resulted in a prolonged accumulation towards steady-state concentrations. No significant changes in the pharmacokinetics of CPT-11, SN-38, or SN-38G were identified; however, the coadministration of selenomethionine significantly reduced the irinotecan biliary index, which has been associated with gastrointestinal toxicity.


CONCLUSIONS
Selenomethionine at 2,200 mug/d did not allow the safe escalation of irinotecan beyond the previously defined MTD of 125 mg/m(2). None of the patients receiving 125 mg/m(2) of irinotecan had grade >2 diarrhea. Unexpected responses and disease stabilizations were noted in a highly refractory population. Further escalation of selenomethionine is recommended in future trials to achieve defined protective serum concentrations of selenium.
Fakih
Marwan G
MG
Department of Medicine, Roswell Park Cancer Institute, Buffalo, NY 14263, USA. marwan.fakih@roswellpark.org
Pendyala
Lakshmi
L
Smith
Patrick F
PF
Creaven
Patrick J
PJ
Reid
Mary E
ME
Badmaev
Vladimir
V
Azrak
Rami G
RG
Prey
Joshua D
JD
Lawrence
David
D
Rustum
Youcef M
YM
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D019540:Area Under Curve; D002166:Camptothecin / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D003967:Diarrhea / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D000077146:Irinotecan; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000139:chemically induced; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D012645:Selenomethionine / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D016896:Treatment Outcome
D000077146:Irinotecan; D012645:Selenomethionine; D002166:Camptothecin