Evaluation of Acute Toxicity and Dosimetric Parameters in High Risk Prostate Cancer Patients Treated by High Radiation Doses

Abstract

For high risk prostate cancer, the treatment volumes and even dose levels are still a controversial issue. The aim of this study is to evaluate the dosemetric parameters and acute toxicity of dose-escalated whole pelvis (WP) Intensity Modulated Radiation Therapy (IMRT) and volumetric modulated arc therapy (VMAT) prostate boost following neoadjuvant and concomitant with androgen deprivation therapy in high-risk prostate cancer patients. This analysis included 73 high-risk prostate cancer patients treated with WP-IMRT followed by boost to the prostate by VMAT to total dose of 80 Gy; between January 2014 and October 2016. Androgen deprivation therapy (ADT) was given for all patients before and during radiation therapy. Drawing the dose volume histograms (DVHs) was done for planning target volumes (PTVs), including Prostate PTV & nodal PTV, and organs at risk including rectum, bladder, femoral heads, and bowel bag for the plans. Acute radiation toxicities were reported during the radiation course and the following 3 months. The DVH analysis showed good coverage of PTVs and organs at risk doses were acceptable. No recorded acute Grade ≥ 3 toxicity. Acute grade 1 toxicity for Gastrointestinal (GI) and Genitourinary (GU) were 65% and 35% respectively, while Grade 2 toxicity was 30% for both. The Proctitis and frequency were the commonest acute toxicity and were maximal during the 5th week of radiation therapy. Dose escalation in two phases utilizing Simultaneous integrated boost (SIB) combined with ADT in high risk prostate cancer patient is feasible and associated with acceptable acute GI and GU toxicity.

An institutional review: dosimetry comparison between simultaneous integrated boost IMRT and VMAT for prostate cancer

“…[5][6][7] This can be achieved using IMRT or VMAT. 8 SIB can be delivered to prostate patients without increasing the risk of acute toxicity. 9 The standard seven gantry angles for prostate IMRT planning technique are 30, 60, 105, 180, 255, 300 and 330.…”

“…4 VMAT offers superior dose homogeneity index (HI), dose gradient index (GI) as compared to IMRT. 8 A better GI shows sharp dose fall near normal tissue which indicates better Organ at risk (OAR) sparing. Although VMAT offers better dosimetric results 10 but there is no final conclusion.…”