Diffusion Tensor Imaging for Characterizing Changes in Triple-Negative Breast Cancer During Neoadjuvant Systemic Therapy

Background: Assessment of treatment response in triple-negative breast cancer (TNBC) may guide individualized care for improved patient outcomes. Diffusion tensor imaging (DTI) measures tissue anisotropy and could be useful for characterizing changes in the tumors and adjacent fibroglandular tissue (FGT) of TNBC patients undergoing neoadjuvant systemic treatment (NAST). Purpose: To evaluate the potential of DTI parameters for prediction of treatment response in TNBC patients undergoing NAST. Study Type: Prospective. Population: Eighty-six women (average age: 51 ± 11 years) with biopsy-proven clinical stage I–III TNBC who underwent NAST followed by definitive surgery. 47% of patients (40/86) had pathologic complete response (pCR). Field Strength/Sequence: 3.0 T/reduced field of view single-shot echo-planar DTI sequence. Assessment: Three MRI scans were acquired longitudinally (pre-treatment, after 2 cycles of NAST, and after 4 cycles of NAST). Eleven histogram features were extracted from DTI parameter maps of tumors, a peritumoral region (PTR), and FGT in the ipsilateral breast. DTI parameters included apparent diffusion coefficients and relative diffusion anisotropies. pCR status was determined at surgery. Statistical Tests: Longitudinal changes of DTI features were tested for discrimination of pCR using Mann–Whitney U test and area under the receiver operating characteristic curve (AUC). A P value <0.05 was considered statistically significant. Results: 47% of patients (40/86) had pCR. DTI parameters assessed after 2 and 4 cycles of NAST were significantly different between pCR and non-pCR patients when compared between tumors, PTRs, and FGTs. The median surface/average anisotropy of the PTR, measured after 2 and 4 cycles of NAST, increased in pCR patients and decreased in non-pCR patients (AUC: 0.78; 0.027 ± 0.043 vs. −0.017 ± 0.042 mm²/s). Data Conclusion: Quantitative DTI features from breast tumors and the peritumoral tissue may be useful for predicting the response to NAST in TNBC. Evidence Level: 1. Technical Efficacy: Stage 4.