B7H3-Targeted Molecular Imaging for Highly Specific Diagnosis and In Vivo Noninvasive Detection of B7H3 in Breast Cancer

B7 homolog 3 (B7H3) is widely expressed in solid tumors, but its role in the diagnosis of breast cancer is unclear. We aimed to evaluate the diagnostic performance of [68Ga]Ga-B7H3-BCH PET/CT in breast cancer patients. Methods: Thirty patients with diverse subtypes of breast cancer underwent both [68Ga]Ga-B7H3-BCH and [18F]FDG PET/CT. Immunohistochemical staining for B7H3 was performed in 25 patients. Results: B7H3 positivity was detected in 84% of samples by immunohistochemistry. [68Ga]Ga-B7H3-BCH demonstrated a higher lesion detection rate compared with [18F]FDG (96.8% vs. 92.4%) among 157 lesions. Median SUVmax was 9.5 in strongly positive lesions; bone metastases had the highest uptake (median SUVmax, 10.9). Imaging resulted in changing the stage or treatment in 8 patients. Hormone receptor–positive/human epidermal growth factor receptor 2–negative lesions showed the highest B7H3 positivity (87.5%) and uptake (median SUVmax, 10.5). Conclusion: [68Ga]Ga-B7H3-BCH PET/CT offers high sensitivity for staging advanced breast cancer and noninvasive B7H3 screening. It may influence clinical decisions and appears to reveal subtype-specific uptake, with a tendency to favor hormone receptor–positive/human epidermal growth factor receptor 2–negative disease.