Association between Apparent Diffusion Coefficient Values on Diffusion Weighted Imaging and Prognostic Factors of Breast Cancer

Objective: To evaluate the association between apparent diffusion coefficient (ADC) values and prognostic factors of breast cancer. Methods: All patients with breast cancer who underwent breast magnetic resonance imaging and subsequent surgery in Kwong Wah Hospital from January 2012 to December 2016 were retrospectively reviewed. The ADC values of the malignant lesions were recorded and compared with tumour size (>= 2 cm, <2 cm), tumour grading (modified Bloom-Richardson-Elston grade 1, 2, 3), tumour aggressiveness (ductal in situ carcinoma and grade 1 invasive carcinomas, grade 2-3 invasive carcinomas), axillary lymph node status (positive, negative), oestrogen receptor expression (positive, negative), progesterone receptor expression (positive, negative), and human epidermal growth factor receptor 2 receptor status (positive, negative). Results: 100 patients with 102 lesions were included in this study, of which 88 were invasive carcinomas and 14 were ductal carcinoma in situ. There was a significant difference between mean ADC value and tumour grading (p < 0.001), with an inverse correlation (Kendall's tau-b = -0339; p < 0.001). The association was independent of other prognostic factors, as shown by multiple linear regression. The mean ADC value of axillary lymph node- positive breast cancers was significantly lower than that of axillary lymph node-negative cancers (p = 0.023), with a significant inverse correlation (r(pb) = -0226; p=0.023), but the association was not independent of other prognostic factors. ADC value showed good predictive value in predicting tumour aggressiveness, with an area under the receiver operating characteristic curve of 0.717. Conclusion: Lower ADC values are well correlated with higher histological grade; therefore, ADC can be considered as a promising prognostic parameter for the evaluation of invasive breast cancer.