Irinotecan Benefits Seen in Three US Trials

ASCO--Pooled data from the three pivotal US phase II studies of irinotecan(Camptosar) show that, at the preferred 125 mg/m² dose, the agenthas consistent antitumor activity and manageable toxicity in patients withpreviously treated metastatic colorectal cancer.

Langdon Miller, MD, of Pharmacia-Upjohn (Kalamazoo, Mich), manufacturerof Camptosar, presented the data at an ASCO scientific session for theCPT-11 Study Group. The studies were the San Antonio Regional Study (48patients), 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 asa 90-minute IV infusion once weekly for four weeks, followed by a two-weekrest. The starting doses ranged from 100 to 150 mg/m².

The overall response by intent-to-treat analysis in these patients withmetastatic disease recurring or progressing during or shortly after priorfluorouracil, was 12.8%. Among those who received the recommended startingdose 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 butnot meeting response criteria.

The mean decrease in CEA was 82% among responders and 28% in patientswith stable disease. Only 6% of patients responding to irinotecan had respondedto prior fluorouracil given for metastatic disease. Twelve responding patientshad baseline tumor pain, and all 12 had decreased pain during irinotecantherapy.