EP-1236: Multiparametric MRI appearance of prostate after androgen deprivation therapy ñ preliminary results

Purpose/Objective: Globally, prostate cancer is responsible for around 250000 deaths annually. Radiotherapy is an effective definitive treatment and, for more aggressive disease, is commonly preceded by neo-adjuvant androgen deprivation therapy (ADT). It has been demonstrated that dose escalated radiotherapy improves biochemical free survival but not overall survival. Further dose escalation is limited by OAR tolerances. Giving a further focal boost to the dominant intra-prostatic lesion (DIPL) appears to be feasible. The DIPL is effectively identified using multi-parametric (MP) MR imaging, however, ADT results in a reduction in prostate and tumour volume and also a loss of contrast on T2w MR images, making lesions less conspicuous. The DIPL is therefore conventionally identified on pre-hormone imaging but it is known that response to therapy is variable and directing a DIPL boost to disease that is resistant to ADT may be most likely to improve clinical outcome. The aim of this work was to compare pre and post treatment imaging to evaluate the feasibility of using post treatment MP-MRI to locate the DIPL. Materials and Methods: Six patients with prostate cancer stage T2b or greater were recruited. All underwent local pre ADT DWI. Patients were imaged post ADT at 1.5 T (Achieva, Philips Medical Systems, Best, The Netherlands) using the cardiac coil. The MR examination included high resolution T2w images, DCE-MRI and diffusion-weighted imaging (DWI). ADC and DCE-MRI parameter maps were calculated on a voxel-by-voxel basis for the whole prostate. Results: Four patients had a clear DIPL pre ADT. This remained largely unchanged in appearance in three cases post ADT, as shown in the example case in the top row of figure 1, where arrows indicate the high flow (left, Fp in ml/ml tissue/min overlayed on T2w imaging), low ADC (right, overlayed on T2w imaging) regions matching those reported as tumour on pre-treatment imaging. In one case the pre ADT DIPL in the right peripheral zone was hard to identify post ADT on T2w imaging (black arrow bottom row, figure 1). However a further lesion in the left anterior gland (white arrow), which was equivocal in appearance pre-treatment, was now conspicuous in both Fp (left) and ADC maps (right).