Diffusion tensor magnetic resonance imaging of breast cancer: associations between diffusion metrics and histological prognostic factors.

OBJECTIVES: To investigate whether quantitative diffusion metrics derived from diffusion tensor imaging (DTI) are associated with histological prognostic factors in breast cancer patients.

METHODS: This retrospective study was approved by the institutional review board, and informed consent was waived. Between 2016 and 2017, 251 consecutive women (mean age, 53.8 years) with breast cancer (230 invasive, 21 in situ) who underwent preoperative magnetic resonance (MR) imaging with DTI were identified. Diffusion gradients were applied in 20 directions (b values, 0 and 1,000 s/mm2 ). DTI metrics - mean diffusivity (MD) and fractional anisotropy (FA) - were measured for breast lesions and contralateral normal breast by two radiologists and were correlated with histological findings using the Mann-Whitney U-test and linear regression analysis.

RESULTS: MD and FA were significantly lower for breast cancers than for normal fibroglandular tissues (1.03 ± 0.25×10-3 mm2 /s vs. 1.60 ± 0.19×10-3 mm2 /s, p < 0.001 and 0.29 ± 0.09 vs. 0.33 ± 0.06, p < 0.001, respectively). Significant differences were observed in MD between invasive cancer and ductal carcinoma in situ lesions (p < 0.001). Multivariate linear analysis showed that larger size (>2 cm) (p = 0.007), high histological grade (grade 3) (p = 0.045) and axillary node metastasis (p = 0.009) were significantly associated with lower MD in invasive breast cancer patients. Larger size (p < 0.001) and high histological grade (p = 0.025) were significantly associated with lower FA.

CONCLUSIONS: DTI-derived diffusion metrics, such as MD and FA, are associated with histological prognostic factors in breast cancer patients.

KEY POINTS: • MD was significantly lower for breast cancers than for normal breast tissues. • FA was significantly lower for breast cancers than for normal breast tissues. • Reduced DTI metrics were associated with poor prognostic factors of breast cancer. • DTI may provide valuable information concerning biological aggressiveness in breast cancer.