Phase II trial of iv 6-thioguanine in advanced colorectal carcinoma.
Oral 6-thioguanine (6-TG) is an S-phase antimetabolite with significant activity against acute leukemia. Preliminary reports of activity of iv 6-TG indicated significant activity against advanced colorectal cancer. We conducted a phase II study of iv 6-TG in 29 patients with advanced measurable colorectal cancer. Only one transient partial response occurred. Toxic effects included mild myelosuppression, nausea, vomiting, and minor ECG changes. We discourage further use of iv 6-TG in the dose and schedule we used to treat advanced colorectal cancer.