The last patient at any given dose level must be observed for 21 days prior to entry of patient at the next dose. If 1 of the initial 3 patients experiences DLT at a given level, 3 additional patients will be added at that dose; if no additional toxicity occurs, escalation resumes. If 2 or more patients at a given dose exhibit DLT, the previous dose is declared the maximum tolerated dose (MTD) and 3 additional patients (6 total) are treated at that dose.