Purpose: To investigate the feasibility and possible clinical utilization of unenhanced diffusion-tensor imaging (DTI) protocol in the diagnostic workup of pregnancy-associated breast cancer (PABC).
Material and Methods: This prospective study was approved by our institutional IRB, and a signed informed consent was obtained from all participants. Since November 2016, seventeen pregnant patients (median gestational age: 19 weeks, range:8-30w) were examined by unenhanced breast MRI protocol. Indications included: newly diagnosed PABC (n=6), follow-up of high-risk patients (n=10) and follow up of neoadjuvant-chemotherapy (NAC) treated patient (n=1). MRI protocol included T2-weighted and DTI sequences, recorded at 1.5T with a total scan duration of ~12min. DTI was acquired using 32 directional diffusion gradients and 0, 700 s/mm2 b-values. DTI parametric maps of the principal diffusion coefficients (λ1,λ2,λ3), mean diffusivity (MD), fractional anisotropy (FA) and maximal anisotropy index (λ1-λ3) were generated and analyzed at pixel resolution. Regions of interest (ROIs) of lesions and the normal fibroglandular tissue were delineated on λ1 maps and were statistically evaluated.
Results: Technically, all scans were completed. One scan was paused due to positional discomfort that, although alleviated by extra supports still resulted in significant artifacts. All other (n=16) scans were of diagnostic quality and artifact-free. All six biopsy-confirmed tumors were detected by DTI maps of λ1, λ2, λ3, MD and λ1-λ3 in agreement with their localization based on clinical/mammographic/sonographic findings. PABC exhibited substantial contrast compared with the apparently normal surrounding pregnancy breast tissue (p<0.001, for all). FA ROIs did not help in differentiating malignant and normal tissues (p=0.48). Scans of high-risk patients did not reveal any new suspicious findings, in agreement with US examinations. Tumor was not identified in the scan of the patient receiving NAC, in agreement with DCE MRI, done several weeks after delivery.
Conclusion: DTI examination is safe, non-invasive, fast and well tolerated by pregnant patients. The significant parametric contrast between normal and malignant tissues, suggests a promising role for DTI in the diagnostic workup of PABC.
