Stereotactic Body Radiotherapy (SBRT) for Prostate Cancer: … · 2014-06-25 · Stereotactic Body...
Transcript of Stereotactic Body Radiotherapy (SBRT) for Prostate Cancer: … · 2014-06-25 · Stereotactic Body...
Stereotactic Body Radiotherapy (SBRT) for Prostate Cancer:Practical Considerations for
Treatment Planning
Minsong Cao, Ph.D.Department of Radiation Oncology
David Geffen School of Medicine at [email protected]
Outline of Presentation• Introduction• Simulation and immobilization• Treatment planning process
– Target and OAR contours– Beam design– Dose optimization/calculation – Plan evaluation
• Patient treatment setup and verification
Learning Objectives
• Summarize and discuss the clinical issues involved when planning prostate patient with SBRT treatment including target volume delineation, contouring critical structure, dose prescription strategies, and plan evaluation
• Summarize and discuss the clinical issues associated plan simulation, motion management and treatment verification for prostate SBRT
SBRT – Prostate
Alongi et al. Radiation Oncology 2013, 8:171
Common treatment techniques• Isocenter
– Isocentric (Linac gantry based) vs. non-isocentric (Cyberknife)
• Beam arrangement– Coplanar vs. non-coplanar beams
– Static gantry angle IMRT vs. Volumetric arc modulated treatment (VMAT)
• PTV dose distribution– Homogenous vs. Heterogeneous vs. Simultaneous boost
Isocentric vs. non-isocentric
Courtesy of BrainLab® Courtesy of Accuray®
PTV dose coverage
Uniform distribution
D. B. FULLER et al., IJROBP. V70(5), 2008
Udrescu et al. Physica Medica.2013( in press)
Clinical Workflow• Patient immobilization and simulation
• Target and organ at risk (OAR) delineation
• Isocenter placement and beam design
• Dose optimization and calculation
• Plan evaluation and quality assurance
• Patient setup and verification
• Treatment delivery
Special considerations - Challenges
• Close proximity of OARs
• High dose gradient / conformity
• Organ motion
Patient immobilization
Body frame
Vacuum bag
CT simulation• Placement of 3 gold markers via trans-rectal ultrasound
• Patient instructed to have comfortably full bladder
• Patient in supine position in the immobilization device
• Non-contrast CT scan and MRI of the pelvis
– from above the iliac crest to below the ischium
– 1.5mm slice thickness
Rectal Balloon
Both S etc. TCR, Vol.1(3), 2012
B L Jones et al, Phys. Med. Biol. 58 (2013)
Spacer between Prostate and Rectum• Biocompatible liquid gel injected between the prostate
and rectum under ultrasound guidance
Alongi et al. Radiation Oncology 2013, 8:171
Target localization
MRI Prostate Anatomy Atlas: http://www.prostadoodle.com/
OAR contours
• Bladder • Rectum• Penile bulb• Femoral heads• Urethra (optional)• Bowel (optional) • Testes (optional)
Planning dose constraints
Descovich et al. JACMP Vol. 14 (5), 2013
Dose conformity and Homogeneity
Feuvret L. et. al., IJROBP, V64(2), 2006
Cyberknife plan• Typical treatments consist of about
100-120 non-coplanar beams• Total treatment 40-60 minutes• Imaging correction every 5–7
beams (about every 30–90s)
Chen et al. Radiation Oncology 2013, 8:58
Cyberknife vs. Linac IMRT• No posterior beams in cyberknife
plan. More anterior beams transvers the bladderHigher bladder dose
• Fewer beams to enter from the left side of patient due to the robotic kinematic constraintsHigher dose to right femur
compared with left femur
Pawlicki et al. Med Dosi 32(2), 2007
Cyberknife vs. Linac IMRT
S. Hossain et al. IJROBP.78(1), 2010
King. Front Radiat Ther Oncol. V43. 2011
Volumetric Modulated Arc for SBRT• Volumetric arc modulated therapy that
simultaneously changes: – Gantry rotation speed– Treatment aperture shape (MLC) – Delivery dose rate
• Improved conformity • Fast plan delivery
Linac VMAT and IMRT plan
Beam parameter selection• Prostate SBRT plans developed for different number of
arcs collimator angels, beam energies and couch rotations for ten patients – Plans with ±45º collimator angles required 38% less
MU with no collimator rotations and 20% less than ±22.5º
– Plans with ±45º collimator angles provided more homogeneous dose distribution
– Plans with two arcs provided improved conformity and homogeneity compared with single arc
Agazaryan N. et. al. ASTRO 2010
Beam parameter selection
• Increasing the number of arcs to 3 did not provide significant improvement
• ±5º couch rotations between arcs did not improve the plan dosimetry significantly
• Selection of beam energy between 6MV and 10MV did not show notable dosimetric difference
Agazaryan N. et. al. ASTRO 2010
Current planning protocol
• Prescription: 8Gy x 5 fractions• Beam energy: 6MV SRS (1000MU/Minute) • Arc: 2 full arcs split to 4 half arcs• Collimator rotation: ±45º • No couch rotation
Plan optimization
• Goals:– PTV:
• V100≥95% R50 < 4.0
– Rectum:• V20Gy < 50% V32Gy < 20%• V36Gy < 10% V40Gy < 5%
– Bladder:• V20Gy < 40% V40Gy<10%
– Femur header: • V16Gy < 5%
Flattering Filter Free (FFF)
MLC Size
Standard MLC HD120 MLC
Plan evaluation – where you stand?
Ruan et. al. Medical Physics, Vol. 39(5), 2012
Ruan et. al. Medical Physics, Vol. 39(5), 2012
Planner
No
Re-plan Plan Evaluation
Yes
Published standards
Treatment Planning
Planning Scripts(Parser)
Patient plan database
Physics Check QA…
Yes
Update
Plan Quality Report
(Planning goals, achieves, ranks)
Cao et. al. AAPM 2013
Dynamic Static
Patient Treatment Setup and Verification
• Patient inter-fractional positioning correction:– 2D image pairs (OBI, ExacTrac …)– 3D volumetric image (CBCT)
• Patient intra-fractional motion tracking: – Electromagnetic tracking (Calypso) – Stereoscopic imaging (ExacTrac)
Prostate moves!
Courtesy of ViewRay®
Kupelian, IJROBP, 67: 1088-1098, 2007
Intra-fractional motion
“If large movements (>5mm) could be excluded by some activecorrection strategies, then the average V100% for the simulated plan could be restored to within approximately 2% of the ideal treatment plans.”
Hossain et al., Med. Phys. 35 (9), 2008
Agazaryan N. et. al. ASTRO 2010
MRI guided radiotherapy
Courtesy of ViewRay®
References1. Alongi, F., et al., Linac based SBRT for prostate cancer in 5 fractions with VMAT and flattening filter
free beams: preliminary report of a phase II study. Radiat Oncol, 2013. 8(1): p. 171.2. Benedict, S.H., et al., Stereotactic body radiation therapy: the report of AAPM Task Group 101. Med
Phys, 2010. 37(8): p. 4078-101.3. Buyyounouski, M.K., et al., Stereotactic body radiotherapy for primary management of early-stage,
low- to intermediate-risk prostate cancer: report of the American Society for Therapeutic Radiology and Oncology Emerging Technology Committee. Int J Radiat Oncol Biol Phys, 2010. 76(5): p. 1297-304.
4. Chen, L.N., et al., Stereotactic body radiation therapy (SBRT) for clinically localized prostate cancer: the Georgetown University experience. Radiat Oncol, 2013. 8: p. 58.
5. Descovich, M., et al., Improving plan quality and consistency by standardization of dose constraints in prostate cancer patients treated with CyberKnife. J Appl Clin Med Phys, 2013. 14(5): p. 162-72.
6. Fuller, D.B., et al., Virtual HDR CyberKnife treatment for localized prostatic carcinoma: dosimetry comparison with HDR brachytherapy and preliminary clinical observations. Int J Radiat Oncol BiolPhys, 2008. 70(5): p. 1588-97.
7. Hossain, S., et al., Simulated real time image guided intrafraction tracking-delivery for hypofractionated prostate IMRT. Med Phys, 2008. 35(9): p. 4041-8.
8. Hossain, S., et al., Dose gradient near target-normal structure interface for nonisocentricCyberKnife and isocentric intensity-modulated body radiotherapy for prostate cancer. Int J RadiatOncol Biol Phys, 2010. 78(1): p. 58-63.
References9. Jones, B.L., et al., Effect of endorectal balloon positioning errors on target deformation and
dosimetric quality during prostate SBRT. Phys Med Biol, 2013. 58(22): p. 7995-8006.10. King, C., Stereotactic body radiotherapy for prostate cancer: current results of a phase II trial.
Front Radiat Ther Oncol, 2011. 43: p. 428-37.11. King, C.R., et al., Long-term outcomes from a prospective trial of stereotactic body radiotherapy
for low-risk prostate cancer. Int J Radiat Oncol Biol Phys, 2012. 82(2): p. 877-82.12. King, C.R., et al., Stereotactic body radiotherapy for localized prostate cancer: pooled analysis
from a multi-institutional consortium of prospective phase II trials. Radiother Oncol, 2013. 109(2): p. 217-21.
13. Kupelian, P., et al., Multi-institutional clinical experience with the Calypso System in localization and continuous, real-time monitoring of the prostate gland during external radiotherapy. Int J Radiat Oncol Biol Phys, 2007. 67(4): p. 1088-98.
14. Pawlicki, T., et al., Investigation of linac-based image-guided hypofractionated prostate radiotherapy. Med Dosim, 2007. 32(2): p. 71-9.
15. Ruan, D., et al., Evolving treatment plan quality criteria from institution-specific experience. Med Phys, 2012. 39(5): p. 2708-12.
16. Udrescu, C., et al., Potential interest of developing an integrated boost dose escalation for stereotactic irradiation of primary prostate cancer. Phys Med, 2014. 30(3): p. 320-5.
Summary|Conclusion• Hypofractionation has the potential to biologically dose-
escalate radiotherapy for prostate cancer.• Establishing SBRT procedures and guidelines from CT
simulation to treatment planning, verification, delivery, and reporting methodology is essential to the success of the implementation of prostate SBRT treatment
• Personal training is another important aspect of implementation of a SBRT prostate program
AcknowledgementsChristopher King, MD, PhDPatrick Kupelian, MDMichael Steinberg, MDDaniel Low, Ph.D. Nzhde Agazaryan, Ph.D.John DeMarco, Ph.D.Steve Tenn, Ph.D.Dan Ruan, Ph.D.Ke Sheng, Ph.D.Chul Lee, M.S.