93P - Assessment of Response to Neoadjuvant Chemotherapy with Diffusion Weighted Imaging at 3T

Abstract

Abstract Purpose To assess radiological tumor response to neoadjuvant chemotherapy (NAC) with Diffusion weighted imaging (DWI) at 3Tesla. Materials and methods 30 patients (mean age 51.4 years) with a histopatholgical verified breast cancer (BIRADS 6) who underwent NAC were included in this prospective IRB approved study. Additionally to routine staging with dynamic contrast enhanced magnetic resonance imaging (CE-MRI) protocol a diffusion weighted sequence with the following parameters was included in the imaging protocol: single-shot, echo-planar imaging sequence with eddy current compensation, a three direction trace diffusion scheme, inversion recovery fat suppression and two b-values of 50 and 850 s/mm2 (TR/TE/TI 13700/83/220ms; FOV 340x117 mm; 40 axial slices; SI 3.5 mm (no gap); matrix 192x64 two averages; spatial resolution, 1.8x1.8x3.5 mm; bandwidth 1446 Hz/pixel; 3:19 min. Patients were examined before the beginning and after 5 or 6 cycles of NAC. In DWI manually drawn ROIs of suspicious areas were assessed for restricted diffusion and apparent diffusion coefficient (ADC) values were calculated. An ADC threshold 1.25x10-3mm2/s was defined as a marker of malignancy. Data were dichotomized and complete response (cr) and partial response (pr) were considered as response and stable disease (sd) and progressive disease (pd) were considered as non-response to NAC. The histopathological assessment of tumor response was used as the standard of reference. Results There were 23 invasive ductal cancers (IDC) and 6 invasive lobular cancers (ILC). Average tumor size was 43.4mm. In the baseline scan one IDC (3%) had an ADC value above the cut-off for malignancy and was excluded. There were 4 (14%) non-responders and 25 (86%) responders. Responders demonstrated an average increase in ADC values of 0.58x10-3mm2/s whereas non-responders failed to show a significant increase in ADC values (average increase 0.09x10-3mm2/s). The classification of DWI as responders and non-responders correlated with histopathological diagnoses of treatment response. Conclusion ADC as an adjunct to conventional CE-MRI is an additional valuable imaging biomarker for the assessment of treatment response to NAC in breast cancer patients. Disclosure All authors have declared no conflicts of interest.