I-123-MIBG myocardial imaging in trastuzumab-based cardiotoxicity: the first experience

Cardiotoxicity related to trastuzumab anticancer treatment poses a diagnostic challenge at early stages. The aim of the present pilot study was to assess the value of iodine-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy in breast cancer patients treated with trastuzumab who showed a decrease in their cardiac function.

I-123-MIBG scintigraphy was performed in nine patients with decreased or significantly decreasing left ventricular ejection fraction (LVEF) during trastuzumab therapy. On the basis of planar images, 4 h heart-to-mediastinum (HMR) ratio and washout percentages (WR) were calculated.

I-123-MIBG scintigraphy revealed abnormal 4 h HMR and increased WR in three patients. LVEF recovery was observed in none of these patients during 3, 6, and 13 months of follow-up. In two of five patients with normal 4 h HMR the washout rates were also normal, whereas in three patients slightly increased washout rates were found. All five patients demonstrated a recovery of their LVEF value during follow-up. One patient with a normal 4 h HMR and normal WR initially showed a significant decrease in LVEF, which decreased further during follow-up. However, the LVEF value remained at 53%, which was within normal limits, after trastuzumab administration.

In this pilot study we have explored the role of I-123-MIBG scintigraphy in the assessment of trastuzumab-related cardiotoxicity and suggest that, in patients with a persistently decreasing LVEF, I-123-MIBG scintigraphy might indicate whether recovery will occur and, consequently, whether retreatment may be initiated.