A Treatment Planning Comparison Of Proton Therapy And Intensity-Modulated Radiotherapy (Imrt) For Prostate Cancer Using The Normal Tissue Complication Probability (Ntcp).

153 Background: The volume of rectum receiving high-dose (i.e. u003e or = 60 Gy) is consistently associated with the risk of Grade u003e or = 2 rectal toxicity or rectal bleeding based on common terminology criteria for adverse events (CTCAE). Our goal was to compare intensity-modulated photon radiotherapy (IMRT) with proton radiotherapy in regard to the rectal dose using the normal tissue complication probability (NTCP). Methods: Between July 2014 and September 2015 the first 10 consecutive low or intermediate risk prostate cancer patients were treated with proton therapy at our institution. All 10 patients were planned with three-dimensional conformal proton therapy (3D-CPT) using two parallel opposed fields as well as comparison IMRT plans. A rectal balloon filled with water was used in all patients treated. Prescribed dose to the prostate was 79.2 Gy or cobalt Gy equivalent (CBE) for protons. Dose-volume histograms were compared. The Lyman-Kutcher-Burman model (n = 0.09, m = 0.13, and TD50 = 76.9 Gy) was used...