Abstract 17680: MIBG Myocardial Scintigraphy is Useful for Predicting CTRCD Caused by Trastuzumab

Introduction: Trastuzumab is known to reduce the mortality rate, recurrence rate, and metastasis rate in Human epidermal growth factor receptor type 2 (HER2)-positive breast cancer patients, and it is recommended to administer it for 12 months to all early-stage HER2-positive breast cancer patients. However, trastuzumab administration can lead to Cancer Therapeutics-Related Cardiac Dysfunction (CTRCD). The guidelines suggest that regular echocardiography every 3 months is useful for early detection of CTRCD, but there are no tests available to predict it before its onset.The purpose of this study is to determine whether cardiac sympathetic nerve evaluation using MIBG myocardial scintigraphy before trastuzumab administration can predict the development of CTRCD three months after administration.

Methods: MIBG myocardial scintigraphy was performed before trastuzumab administration in 35 HER2-positive breast cancer patients, and cardiac function assessment was conducted using echocardiography before administration, at 1 month, and at 3 months. Simultaneously, NT-proBNP and troponin levels were measured. CTRCD was defined as a decrease in global longitudinal strain (GLS) of 10% or more from before administration at the 3-month follow-up.

Results: Anthracycline and trastuzumab regimens were used in 21 patients (60%). CTRCD occurred in 17 patients at the 3-month follow-up. There were no significant differences in age or previous medication between the CTRCD group and the non-CTRCD group, but the early H/M ratio in MIBG myocardial scintigraphy was significantly lower in the CTRCD group (2.77±0.36) compared to the non-CTRCD group (3.10±0.36) (p<0.01). There were no significant differences in the delay H/M ratio or washout rate. None of the echocardiographic parameters, NT-proBNP levels, or troponin levels showed significant differences and did not become predictive factors.

Conclusions: MIBG myocardial scintigraphy is useful for predicting CTRCD caused by trastuzumab. Preclinical studies have suggested that HER2 transactivation from β-adrenergic receptors in the myocardium confers cardioprotection. Suppression of HER2 signaling during cardiac sympathetic nerve dysfunction potentially contributes to the development of CTRCD.