- Arm II: Microinfusion delivery method Cohorts of 3-6 patients receive escalating doses of I 131 MAb 81C6, with dose escalation occurring separately for each arm. After 10 patients are enrolled and the best method of administration is determined, all subsequent patients receive I 131 MAb 81C6 by that method, and the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which no more the 2 of 6 patients experience dose-limiting toxicity.