Biologic target volume delineation and the application of three-dimensional ultrasound image system in hypofractional radiotherapy for prostate cancer.

Abstract

e16585 Background: To investigate the value of magnetic resonance spectroscopy (MRS) and positron emission computed tomography (PET-CT) in biological target volume(BTV) delineation of prostate cancer using hypofractional intensity modulated radiotherapy (HF-IMRT) with simultaneously integrated boost(SIB), and the preliminary efficacy and adverse effects of 3D ultrasound (3DUS) guided imaging in the treatment of prostate cancer using HF-IMRT and SIB. Methods: Between August 2015 and May 2016, 13 patients diagnosed with mid-high risk prostate cancer were retrospectively enrolled. All the eligible patients had underwent MRI MRS and PET-CT(18F-FDG or 11C-CHO) examination before radiotherapy. 5 patients had explicit BTV by examinations mentioned above. Radiation oncologists fused 3DUS and CT images and delineated tumor target volume referring to MRS and PET-CT. The target volumes were named as GTVMRI BTVMRS BTVPET-CT respectively and the volume were recorded. 3DUS guided HF-IMRT were applied during the radiotherapy. Results: The volumes of GTVMRI BTVMRS BTVPET-CT among the 5 patients were different. The mean volume of GTVMRI BTVMRS and BTVPET-CT were 3.52±1.69cm3, 6.64±2.27cm3 and 5.47±2.60cm3,respectively. Significant difference was only observed between GTVMRI and BTVMRS( P = 0.046). Compared to GTVMRI, the average increasing volumes of BTVMRS and BTVPET-CT were 89.07% and 55.52%. The prescription dose and biological effective dose(BED) of BTVMRS were 70.09-73.45Gy and 129.06-135.54Gy. The prescription dose and BED of the whole prostate were 66.02-69.40Gy and 113.32-124.82Gy. The dose of bladder and rectum were within safe control. The prostate specific antigen (PSA) were significantly decreased after radiotherapy. No local recurrence or distant metastasis was observed. Conclusions: MRS and PET-CT can be applied to delineation of the BTV of prostate cancer. With the help of multi-modal image guidance, dose painting for prostate cancer is feasible. 3DUS guided HF-IMRT with SIB is an alternative for radiation oncologists based on BTVMRS. With shortened time and less cost, this technique is safe and non-radioactive compared to CBCT guidance.