OUTLINE: This is a dose escalation, multicenter study. Patients receive oral R115777 for 7-21 days. Patients who achieve complete response (CR) or partial response (PR) following 1-4 courses of treatment may receive up to 4 additional courses. Patients with stable disease may receive another 7-21 day course. If CR or PR is then achieved, patients may receive up to 4 additional courses. Cohorts of 6-12 patients receive escalating doses of R115777 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which between 17% and 33% of patients experience dose limiting toxicity.