Planning target volume margins for prostate radiotherapy using daily electronic portal imaging and implanted fiducial markers

BackgroundFiducial markers and daily electronic portal imaging (EPI) can reduce the risk of geographic miss in prostate cancer radiotherapy. The purpose of this study was to estimate CTV to PTV margin requirements, without and with the use of this image guidance strategy.Methods46 patients underwent placement of 3 radio-opaque fiducial markers prior to prostate RT. Daily pre-treatment EPIs were taken, and isocenter placement errors were corrected if they were ≥ 3 mm along the left-right or superior-inferior axes, and/or ≥ 2 mm along the anterior-posterior axis. During-treatment EPIs were then obtained to estimate intra-fraction motion.ResultsWithout image guidance, margins of 0.57 cm, 0.79 cm and 0.77 cm, along the left-right, superior-inferior and anterior-posterior axes respectively, are required to give 95% probability of complete CTV coverage each day. With the above image guidance strategy, these margins can be reduced to 0.36 cm, 0.37 cm and 0.37 cm respectively. Correction of all isocenter placement errors, regardless of size, would permit minimal additional reduction in margins.ConclusionsImage guidance, using implanted fiducial markers and daily EPI, permits the use of narrower PTV margins without compromising coverage of the target, in the radiotherapy of prostate cancer.

[1]  H. Patrocinio,et al.  An assessment of PTV margin definitions for patients undergoing conformal 3D external beam radiation therapy for prostate cancer based on an analysis of 10,327 pretreatment daily ultrasound localizations. , 2007, International journal of radiation oncology, biology, physics.

[2]  Daniel W. Miller,et al.  Comparison of conventional-dose vs high-dose conformal radiation therapy in clinically localized adenocarcinoma of the prostate: a randomized controlled trial. , 2005, JAMA.

[3]  D. Low,et al.  A critical evaluation of the planning target volume for 3-D conformal radiotherapy of prostate cancer. , 1998, International journal of radiation oncology, biology, physics.

[4]  John Wong,et al.  Assessment of residual error for online cone-beam CT-guided treatment of prostate cancer patients. , 2004, International journal of radiation oncology, biology, physics.

[5]  Qiuwen Wu,et al.  Geometric and dosimetric evaluations of an online image-guidance strategy for 3D-CRT of prostate cancer. , 2006, International journal of radiation oncology, biology, physics.

[6]  J C Stroom,et al.  Internal organ motion in prostate cancer patients treated in prone and supine treatment position. , 1999, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[7]  J A Antolak,et al.  Prostate target volume variations during a course of radiotherapy. , 1998, International journal of radiation oncology, biology, physics.

[8]  Patrick A Kupelian,et al.  Influence of intrafraction motion on margins for prostate radiotherapy. , 2006, International journal of radiation oncology, biology, physics.

[9]  Marco van Vulpen,et al.  Analysis of fiducial marker-based position verification in the external beam radiotherapy of patients with prostate cancer. , 2007, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[10]  F. Sedlmayer,et al.  A strategy for the use of image-guided radiotherapy (IGRT) on linear accelerators and its impact on treatment margins for prostate cancer patients , 2008, Strahlentherapie und Onkologie.

[11]  Jean-François Aubry,et al.  Measurements of intrafraction motion and interfraction and intrafraction rotation of prostate by three-dimensional analysis of daily portal imaging with radiopaque markers. , 2004, International journal of radiation oncology, biology, physics.

[12]  C. Lawton,et al.  Long-term results of the M. D. Anderson randomized dose-escalation trial for prostate cancer , 2009 .

[13]  D Andrew Loblaw,et al.  Individualized planning target volumes for intrafraction motion during hypofractionated intensity-modulated radiotherapy boost for prostate cancer. , 2005, International journal of radiation oncology, biology, physics.

[14]  Karl Bzdusek,et al.  What CTV-to-PTV margins should be applied for prostate irradiation? Four-dimensional quantitative assessment using model-based deformable image registration techniques. , 2008, International journal of radiation oncology, biology, physics.

[15]  T Haycocks,et al.  Positioning errors and prostate motion during conformal prostate radiotherapy using on-line isocentre set-up verification and implanted prostate markers. , 2001, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[16]  M. V. van Herk,et al.  Prostate gland motion assessed with cine-magnetic resonance imaging (cine-MRI). , 2005, International journal of radiation oncology, biology, physics.

[17]  Lei Dong,et al.  Intrafraction prostate motion during IMRT for prostate cancer. , 2001, International journal of radiation oncology, biology, physics.

[18]  Peter Wust,et al.  Potentials of on-line repositioning based on implanted fiducial markers and electronic portal imaging in prostate cancer radiotherapy , 2009, Radiation oncology.

[19]  C. Ling,et al.  Late rectal toxicity after conformal radiotherapy of prostate cancer (I): multivariate analysis and dose-response. , 2000, International journal of radiation oncology, biology, physics.

[20]  M. V. van Herk,et al.  The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy. , 2000, International journal of radiation oncology, biology, physics.

[21]  James M. Balter,et al.  The Influence of Intrafraction Movement on Margins for Prostate Radiotherapy , 2005 .

[22]  Jan J W Lagendijk,et al.  Measurements and clinical consequences of prostate motion during a radiotherapy fraction. , 2002, International journal of radiation oncology, biology, physics.

[23]  David A Jaffray,et al.  On-line aSi portal imaging of implanted fiducial markers for the reduction of interfraction error during conformal radiotherapy of prostate carcinoma. , 2004, International journal of radiation oncology, biology, physics.

[24]  Chris Beltran,et al.  Planning target margin calculations for prostate radiotherapy based on intrafraction and interfraction motion using four localization methods. , 2008, International journal of radiation oncology, biology, physics.

[25]  Joos V Lebesque,et al.  Dose-response in radiotherapy for localized prostate cancer: results of the Dutch multicenter randomized phase III trial comparing 68 Gy of radiotherapy with 78 Gy. , 2006, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.