Phase I trial and pharmacokinetic study of two schedules of vincristine, oral irinotecan, and temozolomide (VOIT) for children with refractory solid tumors: A Children's Oncology Group Phase I Consortium study

Abstract

10017 Background: In preclinical models, temozolomide (TMZ) and vincristine (VCR) are synergistic with irinotecan (IRN). We sought to determine the dose limiting toxicities (DLTs) and maximum tolerated dose (MTD) of orally administered IRN given on two different schedules together with TMZ and VCR in children with refractory solid tumors, using cefixime to reduce IRN-associated diarrhea. Methods: Schedule A: Oral IRN daily for 5 days for 2 weeks (dx5x2), with VCR 1.5 mg/m2 on days 1 and 8 and TMZ 100 mg/m2 on days 1 - 5. Schedule B: Oral IRN daily for 5 days for 1 week (dx5x1) with VCR 1.5 mg/m2 on day 1 and TMZ 100 - 150 mg/m2 on days 1 - 5. Courses were repeated every 3 weeks. A standard cohorts of 3 + 3 design was used. Results: On Schedule A, 18 evaluable patients (median age 15 yrs, range 3 - 21) received 55 courses. At IRN 50 mg/m2/day, 4/12 pts had DLT (hepatotoxicity, abdominal pain, anorexia, hypokalemia, and thrombocytopenia). The oral IRN MTD on this dx5x2 schedule was 35 mg/m2/d (1/6 pts with DLT of hypoalbuminemia). On Schedule B, 18 evaluable patients (median age 9 yrs, range 3–21) received 71 courses of oral IRN 70 - 90 mg/m2/d x 5 with TMZ 100 - 150 mg/m2/d x 5. At oral IRN 90 mg/m2/d with TMZ 150 mg/m2/d, 0/6 pts had DLT, and no Grade 4 toxicities were seen. No further doses were explored. First-course and cumulative toxicity appeared worse with Schedule A, including 3 patients with responding or stable tumors who withdrew due to fatigue, nausea, and weight loss. UGT1A1*28genotype did not correlate with DLT. At the oral IRN MTD of 90 mg/m2/d, the median SN-38 AUCinf was 72 ng/ml*h. One patient with osteosarcoma had a confirmed partial response. Unconfirmed complete and partial responses were seen in 2 Ewing sarcoma patients. Eight additional patients received > 6 courses, including 2 each with neuroblastoma and medulloblastoma. Conclusions: The dx5x1 schedule of VOIT was well tolerated, with SN-38 exposures similar to those achieved with intravenous IRN. Activity on this and prior studies suggests a potential role for VOIT in sarcoma patients. No significant financial relationships to disclose.