Correlations between Apparent Diffusion Coefficient Values and Prognostic Factors of Breast Cancer

Purpose: We investigated possible correlations between apparent diffusion coefficient (ADC) values and prognostic factors of breast cancer. Methods: We retrospectively evaluated 81 patients who underwent magnetic resonance (MR) imaging of the breast and were diagnosed pathologically with invasive ductal carcinoma (IDC) not otherwise specified with invasive foci one cm or larger. We excluded ductal carcinoma in situ and IDC with invasive foci smaller than one cm because small lesions decrease the reliability of signal intensity of diffusion-weighted imaging (DWI). We also excluded special type cancers. We used t-test to compare the mean ADC values of cancers of Stage pT1 (<= 2 cm) versus pT2 or 3 (>2 cm), cancers with versus without vascular invasion, axillary lymph node (N)-positive versus N-negative cancers, estrogen receptor (ER)positive versus ER-negative cancers, and progesterone receptor (PgR)-positive versus PgR-negative cancers. We analyzed correlations between the ADC value with nuclear grade (NG) and human epidermal growth factor receptor 2 (HER2) score by rank test using Spearman's correlation coefficient. Results: The mean ADC value was significantly higher for N-positive (n = 28; 0.97 +/- 0.20 x 10(-3) mm/s) than N-negative cancers (n = 53; 0.87 +/- 0.17 x 10(-3) mm(2)/s) (P=0.017); significantly lower for ER-positive (n = 63; 0.88 +/- 0.15 x 10(-3) mm(2)/s) than ER-negative cancers (n = 18; 1.01 +/- 0.21 x 10(-3) mm(2)/s) (P = 0.005); and significantly lower for PgR-positive (n = 47; 0.88 +/- 0.16 x 10(-3) mm(2)/s) than PgR-negative cancers (n = 34; 0.95 +/- 0.18 x 10(-3) mm(2)/s) (P=0.048). Tumor size, vascular invasion, NG, and HER2 status showed no significant correlation with ADC values. Conclusion: ADC values were higher for N-positive and ER-negative breast cancers than N-negative and ER-positive cancers.