Phase I study of intraperitoneal irinotecan combined with palliative systemic chemotherapy in patients with colorectal peritoneal metastases

Abstract Background Patients with colorectal peritoneal metastases who are not eligible for cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) owing to extensive peritoneal disease have a poor prognosis. It was hypothesized that these patients may benefit from the addition of intraperitoneal irinotecan to standard palliative systemic chemotherapy. Methods This was a classical 3 + 3 phase I dose-escalation trial in patients with colorectal peritoneal metastases who were not eligible for CRS-HIPEC. Intraperitoneal irinotecan was administered every 2 weeks, concomitantly with systemic FOLFOX (5-fluorouracil, folinic acid, oxaliplatin)–bevacizumab. The primary objective was to determine the maximum tolerated dose and dose-limiting toxicities. Secondary objectives were to elucidate the systemic and intraperitoneal pharmacokinetics, safety profile, and efficacy. Results Eighteen patients were treated. No dose-limiting toxicities were observed with 50 mg (4 patients) and 75 mg (9 patients) intraperitoneal irinotecan. Two dose-limiting toxicities occurred with 100 mg irinotecan among five patients. The maximum tolerated dose of intraperitoneal irinotecan was established to be 75 mg, and it was well tolerated. Intraperitoneal exposure to SN-38 (active metabolite of irinotecan) was high compared with systemic exposure (median intraperitoneal area under the curve (AUC) to systemic AUC ratio 4.6). Thirteen patients had a partial radiological response and five had stable disease. Four patients showed a complete response during post-treatment diagnostic laparoscopy. Five patients underwent salvage resection or CRS-HIPEC. Median overall survival was 23.9 months. Conclusion Administration of 75 mg intraperitoneal irinotecan concomitantly with systemic FOLFOX–bevacizumab was safe and well tolerated. Intraperitoneal SN-38 exposure was high and prolonged. As oncological outcomes were promising, intraperitoneal administration of irinotecan may be a good alternative to other, more invasive and costly treatment options. A phase II study is currently accruing.