RecruitingCollection and Measurement of Biomarkers in Prostate Cancer Radiotherapy PatientsThe purpose of this research study is to learn about: 1) How standard radiation treatment to prostate (primary radiotherapy) or the pelvis after prostatectomy (postoperative radiotherapy) may cause changes in MRI and PET imaging traits that might be used in the future to predict response. 2) Comparison of such MRI and PET imaging traits with the number of circulating tumor cells (CTCs) present in the blood prior to treatment and the changes in these counts after treatment. 3) How MRI and PET imaging characteristics and changes are related to the expression of genes in the cancer tissue obtained before treatment from prostate biopsy or a prior prostatectomy before treatment. 4) How the response of prostate cancer treatment relates to the imaging and CTC changes.