Amide proton transfer (APT) imaging of breast cancers and its correlation with biological status

Purpose: To assess the usefulness of amide proton transfer (APT) imaging to predict the biological status of breast cancers. Method: Sixty-six patients (age range 31-85 years, mean 58.9 years) with histopathologically proven invasive ductal carcinomas of 2 cm or larger in diameter were included in this study. 3D APT weighted imaging was conducted on a 3 T scanner. Mean APT signal intensity (SI) was analyzed in relation to biological subtypes, Ki-67 labeling index, and nuclear grades (NGs). Results: The triple-negative (TN) cancers (n = 10; 2.75 +/- 0.42%) showed significantly higher APT SI than the luminal type cancers (n = 48; 1.74 +/- 0.83) and HER2 cancers (n = 8; 1.83 +/- 0.21) (P = 0.0007, 0.03). APT SI had weakly positive correlation with the Ki-67 labeling index (r = 0.38, P = 0.002). The mean APT SIs were significantly higher for high-Ki-67 (>30%) (n = 31; 2.25 +/- 0.70) than low-Ki-67 (<= 30%) cancers (n = 35; 1.60 +/- 0.79) (P = 0.0007). There was no significant difference in the APT SIs between NG 1-2 (n = 31; 1.71 +/- 0.84) and NG 3 (n = 35; 2.08 +/- 0.76%) cancers (P = 0.06). Conclusions: TN and high-Ki-67 breast cancers showed high APT SIs. APT imaging can help to predict the bio-logical status of breast cancers.