Molecular Imaging of HER2 Expression in Breast Cancer patients Using the [^99mTc] Tc-Labeled Small Peptide

Purpose: The accurate determination of human epidermal growth factor receptor 2 (HER2) status can predict response to treatment with HER2-targeted therapy for HER2-positive breast cancer patients. [^99mTc]Tc-HYNIC-(Ser)₃-LTVPWY ([^99mTc]Tc-HYNIC-LY) is a small synthetic peptide molecule targeting of the HER2 receptor. This clinical study evaluated the pharmacokinetic, dosimetry, and efficacy of [^99mTc]Tc-HYNIC-LY for determining the HER2 status in primary breast cancer patients.

Materials and methods: In total, 24 women with suspected primary breast cancer received an intravenous injection of approximately 20 µg (∼740 MBq) of [^99mTc]Tc-HYNIC-LY. In the first 3 patients, blood levels of radioactivity were analyzed for pharmacokinetic evaluation and planar gamma camera imaging was conducted at 30 min and 1, 2, 4, and 24 hour after injection for dosimetry assessment. In the last 21 patients, planar imaging was performed at the baseline, as well as 1, 2, 3, and 4 hour, followed by single-photon emission computed tomography (SPECT) imaging after 4 hour to evaluate the tumor-targeting potential in primary lesions.

Results: Injection of [^99mTc]Tc-HYNIC-LY was safe and well tolerated. Fast blood clearance provided high-contrast HER2 imaging within 1 to 4 hour. The highest absorbed radiation dose was found for kidneys (6.78E-03 ± 2.62E-04 mSv/MBq), followed by the heart (3.73E-03 ± 1.98E-04 mSv/MBq). The [^99mTc]Tc-HYNIC-LY peptide was able to detect HER2 status in primary tumors at an acceptable level.

Conclusion: The findings of this study indicated that [^99mTc]Tc-HYNIC-LY SPECT is safe and feasible for the identification of HER2-positive lesions in primary breast cancer patients, and may provide an accurate and non-invasive modality for guiding HER2 targeted therapy.