In Antimyosin Monoclonal Antibody in the Detection of Doxorubicin Cardiotoxicity: a Comparison with Histology and 99mTc Pyrophosphate

Abstract

Recently, lllIn-antimyosin monoclonal antibidies (IllIn-AMAb) have been introduced for the diagnosis of myocardial infarction. The purpose of this study was to investigate the feasibility of using this agent for the early detection of cardiac damage induced by doxorubicin. The degree of drug induced change in the myocardium was evaluated histologically. 99mTc pyrophosphate (99mTc-PYP), known to preferentially accumulate in Adriamycin caused lesions, was used as a control radiopharmaceutical. Myocardial uptake of 111In-AMAb and 99mTc-PYP was measured in 12 controls and 10 Adriamycin treated rabbits. The results indicated the following: 1) 111In-AMAb uptake in the heart correlated well with the degree of pathology (r=O.95); 2) 99mTc-PYP uptake was also correlated with cardiac damage (r=O.77); 3) The uptake ratio (expressed as percent injected dose per gram myocardial tissue) of Adriamycin treated animals vs. controls was 2.7: 1 for 111In-AMAb and 9.2 for 99mTc-PYP nt 24 and 2 hours after intravenous injection, respectively; 4) considerable non-specific 99mTc_PYP accumulation was measured in the lungs and kidneys and was significantly higher in drug treated animals compared to controls. 111In-AMAb accumulation remained unchanged in these organs. We conclude that 111In-AMAb accurately detects cardiac toxicity induced by Adriamycin but that 99mTc_PYP still remains an acceptable agent in part because, of its availability and higher tracer concentration in the cardiac lesions.