External beam radiotherapy for low-risk prostate cancer

Abstract

Due to widespread screening with prostate-specific antigen (PSA), prostate cancer is diagnosed at an earlier stage, which has led to the so-called stage migration. Consequently, more diagnosed prostate cancers are low-risk disease [1]. The D'Amico criteria are often used to define low-risk patients: typically, they have a PSA level < 10 ng/ml, a biopsy Gleason score ≤ 6, and a clinical T-stage ≤T2a [2]. These criteria are used by the National Comprehensive Cancer Network to create guidelines for the treatment of prostate cancer [3]. Nomograms to predict treatment failure incorporate the same criteria [4, 5]. More recently, the University of California-San Francisco has published and validated the Cancer of the Prostate Risk Assessment (CAPRA) score [1, 6]. The CAPRA score assigns points to different characteristics of the tumor and the patient. PSA level (up to 4 points) and Gleason score (up to 3 points) are considered as the most strong predictors for biochemical recurrence after radical prostatectomy, followed by age, T-stage, and percentage of positive biopsy cores (1 point each). Consequently, the CAPRA score is calculated from 0 to 10 points [1, 7]. Other factors such as PSA doubling time [8], presence of perineural invasion [9-11], and more recently modern imaging such as magnetic resonance imaging (MRI) [12-15], diffusion-weighted MR [16], dynamic contrast-enhanced MR [15], and magnetic resonance spectroscopy (MRS) [16, 17] might further refine the low-risk patient group. Interestingly, the recently updated TNM classification published recognizes the value of additional imaging in T- staging. On page 243 of the 7th edition, they state the following: The following are the procedures for assessing T categories: physical examination, imaging, endoscopy, biopsy and biochemical tests. Although it is not clear how biochemical tests can add to the final T-staging, imaging certainly does.