Image-guided radiotherapy reduces the risk of under-dosing high-risk prostate cancer extra-capsular disease and improves biochemical control

• Main Authors: Per Munck af Rosenschold, Michael J. Zelefsky, Aditya P. Apte, Andrew Jackson, Jung Hun Oh, Elliot Shulman, Neil Desai, Margie Hunt, Pirus Ghadjar, Ellen Yorke, Joseph O. Deasy
• Format: Article
• Language: English
• Published: BMC 2018-04-01
• Series: Radiation Oncology
• Subjects: Image-guided; Radiotherapy; Prostate cancer; High risk disease; IMRT; Tumor control probability
• Online Access: http://link.springer.com/article/10.1186/s13014-018-0978-1

Abstract Background To determine if reduced dose delivery uncertainty is associated with daily image-guidance (IG) and Prostate Specific Antigen Relapse Free Survival (PRFS) in intensity-modulated radiotherapy (IMRT) of high-risk prostate cancer (PCa). Methods Planning data for consecutive PCa patients treated with IMRT (n = 67) and IG-IMRT (n = 35) was retrieved. Using computer simulations of setup errors, we estimated the patient-specific uncertainty in accumulated treatment dose distributions for the prostate and for posterolateral aspects of the gland that are at highest risk for extra-capsular disease. Multivariate Cox regression for PRFS considering Gleason score, T-stage, pre-treatment PSA, number of elevated clinical risk factors (T2c+, GS7+ and PSA10+), nomogram-predicted risk of extra-capsular disease (ECD), and dose metrics was performed. Results For IMRT vs. IG-IMRT, plan dosimetry values were similar, but simulations revealed uncertainty in delivered dose external to the prostate was significantly different, due to positioning uncertainties. A patient-specific interaction term of the risk of ECD and risk of low dose to the ECD (p = 0.005), and the number of elevated clinical risk factors (p = 0.008), correlate with reduced PRFS. Conclusions Improvements in PSA outcomes for high-risk PCa using IG-IMRT vs. IMRT without IG may be due to improved dosimetry for ECD.