Irinotecan and raltitrexed: An active combination in advanced colorectal cancer

Background: Irinotecan and raltitrexed are active agents in metastatic colorectal cancer. Preclinical findings suggest a remarkable synergistic activity between the two drugs and the feasibility of this association has been shown in a recent phase I study. The aim of our phase II trial was to assess the efficacy and tolerability of the combination of irinotecan and raltitrexed in patients with metastatic colorectal cancer untreated with chemotherapy. Patients and methods: From June 1998 to February 2000, 46 patients were enrolled. Patients received irinotecan 350 mg/m² on day 1 and raltitrexed 2.6 mg/m² on day 2, every 3 weeks, for up to nine courses. Tumour assessment was performed every three cycles. Results: A total of 223 cycles of chemotherapy, with a median number of six (range 1-9) courses per patient, was administered. According to intention-to-treat analysis, the overall response rate was 46% (95% confidence interval 31% to 61%). The median duration of response was 21 weeks (range 11-≥101), the median time to progression 27 weeks (range 1-≥116), and the median overall survival 57 weeks (range 1-≥130). The main toxicities were diarrhoea, with National Cancer Institute common toxicity criteria grade 3/4 in 26% of patients, grade 3/4 neutropenia in 20%, grade 3 nausea-vomiting in 13%, grade 3 asthenia in 11% and grade 3/4 transminase elevation in 4%. Conclusions: Results achieved with irinotecan and raltitrexed show that this regimen is active, despite 'not-negligible' toxicity, and may represent a useful regimen for specific subgroups of colorectal cancer patients.