Potential interest of developing an integrated boost dose escalation for stereotactic irradiation of primary prostate cancer

• Published in: Physica medica Vol. 30; no. 3; pp. 320 - 325
• Main Authors: Udrescu, C, Rouvière, O, Enachescu, C, Sotton, M.-P, Bouffard-Vercelli, J, Jalade, P, Chapet, O
• Format: Journal Article
• Language: English
• Published: Italy Elsevier Ltd 01.05.2014
• Subjects: Humans; IMRT; Integrated boost; Magnetic Resonance Imaging; Male; Organs at Risk - radiation effects; Prostate cancer; Prostatic Neoplasms - diagnostic imaging; Prostatic Neoplasms - surgery; Radiation Dosage; Radiology; Radiosurgery - adverse effects; Radiosurgery - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Stereotactic body radiotherapy; Tomography, X-Ray Computed; Stereotactic body radiotherapy; Integrated boost; IMRT; Prostate cancer
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2013.09.005

Abstract Introduction The stereotactic irradiation is a new approach for low-risk prostate cancer. The aim of the present study was to evaluate a schema of stereotactic irradiation of the prostate with an integrated-boost into the tumor. Material and methods The prostate and the tumor were delineated by a radiologist on CT/MRI fusion. A 9-coplanar fields IMRT plan was optimized with three different dose levels: 1) 5 × 6.5 Gy to the PTV1 (plan 1), 2) 5 × 8 Gy to the PTV1 (plan 2) and 3) 5 × 6.5 Gy on the PTV1 with 5 × 8 Gy on the PTV2 (plan 3). The maximum dose (MaxD), mean dose (MD) and doses received by 2% (D2), 5% (D5), 10% (D10) and 25% (D25) of the rectum and bladder walls were used to compare the 3 IMRT plans. Results A dose escalation to entire prostate from 6.5 Gy to 8 Gy increased the rectum MD, MaxD, D2, D5, D10 and D25 by 3.75 Gy, 8.42 Gy, 7.88 Gy, 7.36 Gy, 6.67 Gy and 5.54 Gy. Similar results were observed for the bladder with 1.72 Gy, 8.28 Gy, 7.01 Gy, 5.69 Gy, 4.36 Gy and 2.42 Gy for the same dosimetric parameters. An integrated SBRT boost only to PTV2 reduced by about 50% the dose difference for rectum and bladder compared to a homogenous prostate dose escalation. Thereby, the MD, D2, D5, D10 and D25 for rectum were increased by 1.51 Gy, 4.24 Gy, 3.08 Gy, 2.84 Gy and 2.37 Gy in plan 3 compared to plan 1. Conclusions The present planning study of an integrated SBRT boost limits the doses received by the rectum and bladder if compared to a whole prostate dose escalation for SBRT approach.