The role of mean diffusivity (MD) as a predictive index of the response to chemotherapy in locally advanced breast cancer: a preliminary study

To evaluate the role of mean diffusivity (MD) as a predictive index of the response to chemotherapy in locally advanced breast cancer. Twenty-one women referred to our institution with a diagnosis of locally advanced breast cancer underwent magnetic resonance imaging (MRI) studies at 1.5 T before beginning and after completing combined neoadjuvant chemotherapy. The examination protocol included an EPI sequence sensitised to diffusion (b-value 1,000 s/mm2) and three-dimensional (3D) coronal T1 sequences before and after intravenous contrast medium. Tumours were delineated by using dynamic MR acquisition before and after chemotherapy. The percentage of tumour volume reduction (PVR) and pre-(MDpre) and post-therapy (MDpost) MD values were computed for each lesion. PVR ≥ 65% was observed in 17/21 patients (responders). MDpre of responders (0.99 ± 0.27 10-3 mm2/s) was significantly (p = 0.025) lower than MDpre of non-responders (1.46 ± 0.33 10-3 mm2/s). Moreover, in patients as a whole PVR significantly correlated (p = 0.01, r = -0.54) with MDpre. MDpost (1.26 ± 0.39 10-3 mm2/s) of responders was significantly(p = 0.024) higher than MDpre (0.99 ± 0.27 mm2 10-3 mm2/s), whereas non-responders MDpost (1.00 ± 0.14 10-3 mm2/s)did not increase compared with MDpre (1.46 ± 0.33 10-3 mm2/s). This preliminary study seems to indicate that low values of pre-chemotherapy MD may identify, before starting treatment, the patients with higher probability of response in terms of percentage of volume reduction of the lesion. MD may represent a complementary parameter useful to correctly select patients for neoadjuvant chemotherapy. (orig.)