title: Quantification of the margin required for treating intraprostatic lesions.
abstract: Advances in magnetic resonance imaging (MRI) sequences allow physicians to define the dominant intraprostatic lesion (IPL) in prostate radiation therapy treat-ments allowing for dose escalation and potentially increased tumor control. This work quantifies the margin required around the MRI-defined IPL accounting for both prostate motion and deformation. Ten patients treated with a simultaneous integrated intraprostatic boost (SIIB) were retrospectively selected and replanned with incremental 1 mm margins from 0-5 mm around the IPL to determine if there were any significant differences in dosimetric parameters. Sensitivity analysis was then performed accounting for random and systematic uncertainties in both prostate motion and deformation to ensure adequate dose was delivered to the IPL. Prostate deformation was assessed using daily CBCT imaging and implanted fiducial markers. The average IPL volume without margin was 2.3% of the PTV volume and increased to 11.8% with a 5 mm margin. Despite these changes in vol-ume, the only statistically significant dosimetric difference was found for the PTV maximum dose, which increased with increasing margin. The sensitivity analysis demonstrated that a 3.0 mm margin ensures > 95% IPL coverage accounting for both motion and deformation. We found that a margin of 3.0 mm around the MRI defined IPL is sufficient to account for random and systematic errors in IPL posi-tion for the majority of cases.
authors.affiliation: University of Miami Miller School of Medicine. m.studenski@med.miami.edu.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Studenski
authors.forename: Yanisley
authors.initials: Y
authors.lastname: Valenciaga
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Abramowitz
authors.forename: Radka
authors.initials: R
authors.lastname: Stoyanova
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Bossart
authors.forename: Nesrin
authors.initials: N
authors.lastname: Dogan
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D019583:Dose Fractionation, Radiation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012189:Retrospective Studies