Indium-111-antimyosin scintigraphy after doxorubicin therapy in patients with advanced breast cancer Indium-111-antimyosin (111In-antimyosin) scans were performed in 20 women with advanced breast cancer after 10 cycles of chemotherapy consisting of cyclophosphamide, 5-fluorouracil and doxorubicin (total cumulative dose of doxorubicin of 500 mg/m2). Antimyosin uptake in the myocardium was quantified by means of a heart-to-lung ratio (HLR). Antimyosin uptake in the myocardium was observed in 17/20 (85%) patients, and HLR after chemotherapy was 1.86 +/- 0.25. Left ventricular ejection fraction (EF) was determined before and after chemotherapy. Patients with decreased EF (8/20, 40%) presented with more intense antimyosin uptake (HLR of 2.11 +/- 0.10 versus 1.70 +/- 0.16 (p = 0.01]. HLR values correlated with EF values after chemotherapy (r = -0.47, p less than 0.05). Positive antimyosin studies after chemotherapy including doxorubicin, indicate the presence of myocardial damage in these patients. Antimyosin studies are a sensitive method to detect myocyte damage in patients after doxorubicin therapy. 