Myocardial HER2 expression with 111In-DTPA-trastuzmab scan in patients shortly after anthracycline treatment
3057 Background: The monoclonal antibody trastuzumab, apart from antitumor effect, can induce cardiotoxicity, particularly when combined with anthracyclines. Myocardial HER2 upregulation may serve, transiently, as a compensatory mechanism induced by cardiac stress. Previously we showed in a xenograft model that 111In-DTPA-trastuzumab scintigraphy can detect HER2 positive lesions (Br J Pharmacol 2004;143:99–106) but that myocardial 111In-DTPA-trastuzumab uptake was found in only 1 of 17 anthracycline-pretreated HER2-positive metastatic breast cancer patients (ESMO 2004#50). This low number may be related to the long interval between anthracycline administration (median 11 months) and performed scan in these patients. To evaluate whether myocardial HER2 expression is induced by anthracyclines, we performed 111In-DTPA-trastuzumab scans in patients shortly after anthracycline treatment. Methods: Patients who completed 4–6 cycles of anthracycline-based chemotherapy (< 3 weeks after last dose) underwent gammacamera imaging 48 and 96 h after iv administration of 150 MBq 111In-DTPA-trastuzumab (5mg). Results: 10 anthracycline-treated patients, 8 as adjuvant breast cancer treatment and 2 for metastatic sarcoma have been enrolled. Myocardial 111In-DTPA-trastuzumab uptake was observed in 5/10 anthracycline-treated patients who all were without symptomatic cardiac dysfunction. Conclusions: Shortly after completion of anthracycline treatment myocardial HER2 overexpression was detectable in 50% of the patients. This may be a transient phenomenon. 111In-DTPA-trastuzumab scan after anthracycline treatment prior to adjuvant trastuzumab may identify patients more susceptible for trastuzumab-induced cardiotoxicity. This important observation may add to optimal timing of trastuzumab therapy i.e. when HER2/neu expression in the heart is negative (again). [Table: see text]