Anderle, K.

Durante, M.

Graeff, C.

Greco, C.

Pimentel, N.

Stroom, J.

GSI Repository

An in silico Trial of X-rays vs Carbon Ions in Lung Cancer RadiosurgeryK. Anderle1, J. Stroom2, N. Pimentel2, C. Greco2, M. Durante1, and C. Graeff11GSI, Darmstadt, Germany; 2Fundac¸a˜o Champalimaud, Lisbon, PortugalIntroductionStereotactic body radiotherapy (SBRT) with photons totreat extra-cranial tumors in a single fraction has beenshown to yield local control rates > 80 % with acceptabletoxicity [1]. Scanned particle therapy (PT) has proven itsefficacy for head and neck tumors, while treatment of mo-bile tumors of the lung is still challenging due to interplayand range changes. We performed an in silico case studycomparing SBRT and PT (carbon ions) in lung cancer pa-tients to investigate potential benefits of PT in radiosurgery.Materials and methodsWe used data of nine patients that were actually treatedwith SBRT at Fundac¸a˜o Champalimaud, Lisbon. The pre-scribed target dose is at least 24 Gy for 99 % of the targetvolume, with strict adherence to dose constraints for organsat risk (OAR). The actual SBRT treatment plans are com-pared to simulated treatment with PT using TRiP98 [2] ona 4D-CT. For SBRT, isotropic ITV-PTV margins of 3 mmwere used. Due to range changes in PT we added margins3 mm laterally and 1 mm in beam’s eye view on CTV andthen computed a range-considering ITV with 2 mm + 2 %range margins. Five times slice-by-slice rescanning wasused to counter interplay.Figure 1: Dose cuts for SBRT (left) and PT (right) in twopatients. The first patient (top) shows a favorable dose dis-tribution of PT, while the second case (bottom) appears bet-ter suited for SBRT.ResultsAverage peak to peak tumor motion was 5.6 mm (from0.2 mm to 9.5 mm). Comparison of dose cuts betweenSBRT and PT is shown in Figure 1. Both therapies pro-vided excellent target coverage and OAR doses within tol-erances, except for three patients, where maximal allowedpoint dose in smaller airways was exceeded due to tumorproximity. Differences between SBRT and PT in dose de-position for 7 specific OAR are shown in Figure 2. Onaverage all OAR receive less dose in PT, except for ipsi-lateral lung D10%. The most profound difference was inspinal cord and ipsilateral lung D10%, where the averagedose difference was 4.2 Gy and -4.5 Gy, respectively.DiscussionThe results clearly indicate potential of PT in treatinglung cancer. With smaller entry channel than SBRT, PT candeposit less dose in OAR, while maintaining same targetcoverage. This advantage varies with patient anatomy andlesion location, motion and size. The clinical relevance ofpossible further dose escalation or improved OAR sparingwith scanned carbon ion therapy needs to be validated. Thisstudy will include a total of 20 patients, and also furtherinvestigate the robustness of PT.Figure 2: Box-and-whisker plot for dose difference be-tween SBRT and PT for different OAR. Boxes contain databetween 25 % and 75 %, dashed lines represent mean valueand whiskers minimum and maximum values.References[1] Greco C, Zelefsky MJ, Lovelock M, et al. Predictors of localcontrol after single-dose stereotactic image-guided intensity-modulated radiotherapy for extracranial metastases. Int J Ra-diat Oncol Biol Phys 2011; 79:1151-1157.[2] Richter D, Schwarzkopf A, Trautmann J, et al. Upgrade andbenchmarking of a 4D treatment planning system for scannedion beam therapy. Med Phys 2013; 40:051722.BIOPHYSICS-26 GSI SCIENTIFIC REPORT 2013228 doi:10.15120/GR-2014-1-BIOPHYSICS-26

An in silico Trial of X-rays vs Carbon Ions in Lung Cancer Radiosurgery

http://repository.gsi.de/record/67931/files/BIOPHYSICS-26.pdf

An in silico Trial of X-rays vs Carbon Ions in Lung Cancer Radiosurgery

Abstract

Similar works

Full text

Available Versions

GSI Repository