Myocardial iodine-labeled metaiodobenzylguanidine 123 uptake relates to age

123I-labeled metaiodobenzylguanidine (123I-MIBG) is used increasingly to assess cardiac adrenergic neuron function. Few studies have reported data on myocardial MIBG uptake in relation to age, with contradictory results. This study reports the results of myocardial MIBG studies in untreated patients with cancer to assess the influence of age on myocardial MIBG uptake.

Thirty-nine patients with cancer enrolled in a study to assess the effect of doxorubicin administration on adrenergic neuron function underwent baseline studies with 123I-MIBG before chemotherapy. None of the patients had a history of neuropathy, previous cardiac disease, or previous chemotherapy or mediastinal radiotherapy. Myocardial MIBG uptake was quantified by a heart/mediastinal ratio (HMR) 4 hours after intravenous administration of 5 mCi 123I-MIBG. The mean age of patients was 38 years, ranging from 16 to 75 years. Ten patients were below 20 years, 13 patients were between 20 and 40 years, six patients were between 40 and 60 years, and 10 patients were greater than 60 years of age. Myocardial 123I-MIBG uptake was observed in all patients, with a mean HMR of 1.85 +/- 0.29 (range 1.31 to 2.62). HMR correlated with age (r = -0.6264; p < 0.001). A decrease in 123I-MIBG uptake with aging was observed. The mean HMR of patients of less than 20 years was 2.07, of patients between 20 and 40 years 1.89, of patients between 40 and 60 years 1.83, and of patients greater than 60 years 1.56. The best separation was observed comparing patients who were greater than 60 years (mean HMR 1.56 +/- 0.16; range 1.31 to 1.78) with patients who were less than 60 years of age (mean HMR 1.95 +/- 0.24; range 1.56 to 2.62; p = 0.003).

Myocardial 123I-MIBG uptake relates to age. A decrease in myocardial MIBG uptake is observed with aging, especially in those patients over 60 years of age. The influence of age on myocardial MIBG uptake has to be taken into account when studies are designed to assess cardiac adrenergic neuron function with 123I-MIBG.