title: Individualized margins for prostate patients using a wireless localization and tracking system.
abstract: This study investigates the dosimetric benefits of designing patient-specific margins for prostate cancer patients based on 4D localization and tracking. Ten prostate patients, each implanted with three radiofrequency transponders, were localized and tracked for 40 fractions. "Conventional margin" (CM) planning target volumes (PTV) and PTVs resulting from uniform margins of 5 mm (5M) and 7 mm (7M) were explored. Through retrospective review of each patient's tracking data, an individualized margin (IM) design for each patient was determined. IMRT treatment plans with identical constraints were generated for all four margin strategies and compared. The IM plans generally created the smallest PTV volumes. For similar PTV coverage, the IM plans had a lower mean bladder (rectal) dose by an average of 3.9% (2.5%), 8.5% (5.7%) and 16.2 % (9.8%) compared to 5M, 7M and CM plans, respectively. The IM plan had the lowest gEUD value of 23.8 Gy for bladder, compared to 35.1, 28.4 and 25.7, for CM, 7M and 5M, respectively. Likewise, the IM plan had the lowest NTCP value for rectum of 0.04, compared to 0.07, 0.06 and 0.05 for CM, 7M and 5M, respectively. Individualized margins can lead to significantly reduced PTV volumes and critical structure doses, while still ensuring a minimum delivered CTV dose equal to 95% of the prescribed dose.
authors.affiliation: University of Utah. prema.rassiah-szegedi@hci.utah.edu.
authors.forename: Prema
authors.initials: P
authors.lastname: Rassiah-Szegedi
authors.forename: Brian
authors.initials: B
authors.lastname: Wang
authors.forename: Martin
authors.initials: M
authors.lastname: Szegedi
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tward
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao
authors.forename: Y Jessica
authors.initials: YJ
authors.lastname: Huang
authors.forename: Vikren
authors.initials: V
authors.lastname: Sarkar
authors.forename: Dennis
authors.initials: D
authors.lastname: Shrieve
authors.forename: Bill
authors.initials: B
authors.lastname: Salter
mesh_terms: D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects*; D012189:Retrospective Studies; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000528:radiation effects*