ASCO--Pooled data from the three pivotal US phase II studies of irinotecan(Drug information on irinotecan) (Camptosar) show that, at the preferred 125 mg/m² dose, the agent has consistent antitumor activity and manageable toxicity in patients with previously treated metastatic colorectal cancer.
Langdon Miller, MD, of Pharmacia-Upjohn (Kalamazoo, Mich), manufacturer of Camptosar, presented the data at an ASCO scientific session for the CPT-11 Study Group. The studies were the San Antonio Regional Study (48 patients), the Mayo North Central Cancer Treatment Group (90 patients), and the US Multicenter Study Group (166 patients).
The trials involved 304 patients, all of whom received irinotecan as a 90-minute IV infusion once weekly for four weeks, followed by a two-week rest. The starting doses ranged from 100 to 150 mg/m².
The overall response by intent-to-treat analysis in these patients with metastatic disease recurring or progressing during or shortly after prior fluorouracil(Drug information on fluorouracil), was 12.8%. Among those who received the recommended starting dose of 125 mg/m², the response rate was 15% (2 CR; 27 PR), and 56% had a best response of stable disease, often with tumor reductions but not meeting response criteria.
The mean decrease in CEA was 82% among responders and 28% in patients with stable disease. Only 6% of patients responding to irinotecan had responded to prior fluorouracil given for metastatic disease. Twelve responding patients had baseline tumor pain, and all 12 had decreased pain during irinotecan therapy.