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Image-guided robotic stereotactic radiation therapy with fiducial-free tumor tracking for lung cancer.

ABSTRACT: Stereotactic body radiation therapy (SBRT) for early-stage lung cancer can be achieved with several methods: respiratory gating, body frame, or real-time target and motion tracking. Two target tracking methods are currently available with the CyberKnife® System: the first one, fiducial tracking, requires the use of radio-opaque markers implanted near or inside the tumor, while the other, Xsight® Lung Tracking System, (XLTS) is fiducial-free. With XLTS, targeting is synchronized directly with target motion, which occurs due to respiration. While the former method (fiducial tracking) is well documented, the clinical relevance of the latter (tracking without fiducials) has never been well described to this date.A study was performed at our department for each patient treated for lung cancer with CyberKnife using XLTS. Selection criteria were: primary or recurring T1 or T2 stage non-small-cell lung cancer (NSCLC) with 15-60 mm tumor size. Initial staging included CT-Scan and FDG-PET.Fifty-one patients not amenable to surgery were treated with XLTS. Median follow-up was 15 months (range, 5-30 months). Median tumor size was 24 mm (range, 15-60 mm). Median total dose was 60 Gy (36-60 Gy) in three fractions. Actuarial overall survival was 85.5% (95% CI = 74.5-96%) at 1 year and 79.4% (95% CI = 64-94.8%) at 2 years. Actuarial local control rate was 92% (95% CI = 84-99%) at one 1 year and 86% (95% CI = 75-97%) at 2 years.Local control and overall survival rates were similar to previous reports that used fiducials for tumor tracking. Toxicity was lower than most studies since tumor tracking did not require fiducial implantion. This fiducial-free method for respiratory motion tracking is a valid option for the most fragile patients.

SUBMITTER: Bibault JE

PROVIDER: S-EPMC3432006 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Image-guided robotic stereotactic radiation therapy with fiducial-free tumor tracking for lung cancer.

Bibault Jean-Emmanuel JE Prevost Bernard B Dansin Eric E Mirabel Xavier X Lacornerie Thomas T Lartigau Eric E

Radiation oncology (London, England) 20120624

<h4>Purpose</h4>Stereotactic body radiation therapy (SBRT) for early-stage lung cancer can be achieved with several methods: respiratory gating, body frame, or real-time target and motion tracking. Two target tracking methods are currently available with the CyberKnife® System: the first one, fiducial tracking, requires the use of radio-opaque markers implanted near or inside the tumor, while the other, Xsight® Lung Tracking System, (XLTS) is fiducial-free. With XLTS, targeting is synchronized d ...[more]

PMID: 22726884

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Project description:PurposeAccurate verification of tumor position during irradiation could reduce the probability of target miss. We investigated whether a commercial gantry-mounted 2-dimensional (2D) kilo-voltage (kV) imaging system could be used for real-time 3D tumor tracking during volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT). Markerless tumor tracking on kV fluoroscopic images was validated using a life-like moving thorax phantom and subsequently performed on kV images continuously acquired before and during free-breathing VMAT lung SBRT.Methods and materialsThe 3D-printed/molded phantom containing 3 lung tumors was moved in 3D in TrueBeam developer mode, using simulated regular/irregular breathing patterns. Planar kV images were acquired at 7 frames/s during 11 Gy/fraction 10 MV flattening filter free VMAT. 2D reference templates were created for each gantry angle using the planning 4D computed tomography inspiration phase. kV images and templates were matched using normalized cross correlation to determine 2D tumor position, and triangulation of 2D matched projections determined the third dimension. 3D target tracking performed on cone beam computed tomography projection data from 18 patients (20 tumors) and real-time online tracking data from 2 of the 18 patients who underwent free-breathing VMAT lung SBRT are presented.ResultsFor target 1 and 2 of the phantom (upper lung and middle/medial lung, mean density -130 Hounsfield units), 3D results within 2 mm of the known position were present in 92% and 96% of the kV projections, respectively. For target 3 (inferior lung, mean density -478 Hounsfield units) this dropped to 80%. Benchmarking against the respiratory signal, 13/20 (65%) tumors (10.5 ± 11.1 cm3) were considered successfully tracked on the cone beam computed tomography data. Tracking was less successful (≤50% of the time) in 7/20 (1.2 ± 1.5 cm3). Successful online tracking during lung SBRT was demonstrated.Conclusions3D markerless tumor tracking on a standard linear accelerator using template matching and triangulation of free-breathing kV fluoroscopic images was possible in 65% of small lung tumors. The smallest tumors were most challenging.

Dataset Information

Image-guided robotic stereotactic radiation therapy with fiducial-free tumor tracking for lung cancer.

Publications

Image-guided robotic stereotactic radiation therapy with fiducial-free tumor tracking for lung cancer.

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