Single-agent irinotecan as second-line weekly chemotherapy in elderly patients with advanced colorectal cancer

Irinotecan is a standard option for relapsed/refractory advanced colorectal cancer. Although in a recently reported, randomized trial it was found that a regimen of irinotecan once every 3 weeks was associated with a lower incidence of severe diarrhea than with weekly treatment with similar efficacy, there is no evidence in the literature that suggests the optimal dosing strategy for the drug, along with treatment efficacy and safety, following 5-fluorouracil/oxaliplatin-based chemotherapy in elderly patients. A phase II study has reported significantly reduced toxicity when irinotecan was administered once a week for 2 weeks, followed by a week rest.

From January 2004 to April 2005, we analyzed, retrospectively, our data on single-agent irinotecan as a second-line chemotherapy in elderly patients (> or =70 years) with advanced colorectal cancer. Twenty-three patients were evaluated. CPT-11 (80 mg/m2) was given as a 60-min intravenous infusion in repeated 21-day courses comprising weekly treatment for 2 consecutive weeks followed by a 1-week rest. Tumor measurements were obtained after every third course of therapy. Toxicity was assessed weekly using the National Cancer Institute Common Toxicity Criteria, version 2.

The median number of treatment courses received per patient was 4 (range, 1-8). All patients were assessable for toxicity and 21 for response. The most frequently observed severe toxicities were diarrhea (grade 3, 13%) and neutropenia (grade 3, 30.4%; grade 4, 8.6%). Only 1 case of neutropenic fever occurred. Other hematological and non-hematological toxicities were mild and manageable. Objective partial responses were observed in 3 patients (13%). An additional 10 patients (43%) had stable disease as their best response. To date, 12 patients have progressed with a median time-to-progression of 4.3 months and a median survival of 8.3 months.

A weekly irinotecan administration can induce tumor control in elderly patients with advanced colorectal cancer that has progressed during or shortly after 5-fluorouracil/oxaliplatin-based chemotherapy. However, a careful monitoring of hematological toxicity and special instructions to prevent and manage diarrhea are mandatory in this setting of patients.