title: Predictors of toxicity in treating patients with neuroblastoma by radiolabeled metaiodobenzylguanidine.
abstract: We searched for methods that would enable prescriptions of the maximum tolerable doses of iodine-131 metaiodobenzylguanidine (MIBG) and iodine-125 MIBG in the treatment of patients with neuroblastoma. We correlated doses, defined in different ways, with subsequent platelet levels in treated patients to determine accurate predictors of the most frequent toxicity, thrombocytopenia. Nine patients with neuroblastoma were given 131I-MIBG (4.9-8.1 GBq or 132-220 mCi) and ten were given 125I-MIBG (8.3-30.0 GBq or 224-809 mCi) as initial treatments. These therapies were sufficiently varied that correlations could be made between indices of the doses and the subsequent toxicity as reflected in circulating platelet levels. Predictors of toxicity were: whole-body absorbed dose of radiation (cGy) calculated from pretherapy tracer doses of 131I-MIBG; GBq/kg of body weight; and GBq/m2 of body surface area. Toxicity was recorded as the nadir of the platelet level and platelet/pretherapeutic level (platelet ratio). For treatments with 131I-MIBG, the highest correlation was obtained between cGy and the log10-transformed platelet ratio (r = -0.86), but comparison of GBq/m2 and the platelet nadir (r = -0.76) or the platelet ratio (r = -0.74) or the log10 transformed platelet ratio (r = -0.73) gave comparable and statistically significant results. For treatments with 125I-MIBG, significant correlations were obtained between GBq/m2 and the platelet ratio (r = -0.81) or GBq/kg and the log10-transformed platelet ratio; the correlation between cGy and any toxicity index was low. Per administered GBq, 131I-MIBG was 2.6 times more potent than 125I-MIBG in causing a platelet ratio of 0.1.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028.
authors.forename: J C
authors.initials: JC
authors.lastname: Sisson
authors.forename: B
authors.initials: B
authors.lastname: Shapiro
authors.forename: R J
authors.initials: RJ
authors.lastname: Hutchinson
authors.forename: J E
authors.initials: JE
authors.lastname: Carey
authors.forename: K R
authors.initials: KR
authors.lastname: Zasadny
authors.forename: S A
authors.initials: SA
authors.lastname: Zempel
authors.forename: D P
authors.initials: DP
authors.lastname: Normolle
mesh_terms: D019797:3-Iodobenzylguanidine; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D007462:Iodobenzenes / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D009447:Neuroblastoma / Q000188:drug therapy*; D011879:Radiotherapy Dosage; D013921:Thrombocytopenia / Q000209:etiology* / Q000517:prevention & control
chemical_list: D000970:Antineoplastic Agents; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019797:3-Iodobenzylguanidine