MRI-guided localization of the dominant intraprostatic lesion and dose analysis of volumetric modulated arc therapy planning for prostate cancer.

Abstract

Primary radiation therapy is acurative treatment option for prostate cancer. The aim of this study was to evaluate the detection of the dominant intraprostatic lesion (DIL) with magnetic resonance imaging (MRI) for radiotherapy treatment planning, the comparison with transrectal ultrasound (TRUS)-guided biopsies and the examination of the dose distribution in relation to the DIL location. In all, 54patients with treatment planning MRI for primary radiotherapy of prostate cancer from 03/2015 to 03/2017 at the Universitätsklinikum Würzburg were identified. The localization of the DIL was based on MRI with T2- and diffusion-weighted imaging. After registration of the MR image sets within Pinnacle3 (Philips Radiation Oncology Systems, Fitchburg, WI, USA), the dose distribution was analyzed. The location of the DIL was compared to the pathology reports in aside-based manner. The DIL mean dose (Dmean) was 77.51 ± 0.77 Gy and in 50/51cases within the tolerance range or exceeded the prescribed dose. There was asignificant difference in Dmean between ventral (n = 21) and dorsal (n = 30) DIL (77.87 ± 0.67 vs. 77.26 ± 0.77 Gy; p = 0.005). MRI-guided localization showed an accuracy and sensitivity of up to 78.8% and 82.1% for inclusion of secondary lesions, respectively. Up to 82.1% of histologically verified intraprostatic lesions were identified in the context of MRI-guided radiotherapy treatment planning. As expected, dorsal DIL tend to be minimally underdosed in comparison to ventral DIL. Adequate dose coverage was achieved in over 98% of patients.