The study will be conducted in 2 phases. During the first, Dose Escalation Phase, eligible patients wil be assigned in groups of 3-6 (depending upon the treatment response seen at each dose) to dose cohorts of between 2-5 weekly IV doses of 131I-TM601. Escalation to the next highest dose during the Dose Escalation Phase will be dependent upon demonstrated tolerance in the previous dosing group. In the second, Efficacy Phase, all patients will be treated with the Maximum Tolerated Dose determined in the Dose Escalation Phase.