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SBRT in the Everyday Clinical Setting

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					SBRT IN THE EVERYDAY CLINICAL SETTING
William H. Hinson, Ph.D. Department of Radiation Oncology Wake Forest University Baptist Medical Center Winston-Salem, N.C.

SBRT Team at WFUBMC
Physician  Volker Stieber  William Blackstock  Kevin McMullen Physics  William H. Hinson  William T. Kearns Whole cast of support staff

Essentials for SBRT
3-D Imaging device Treatment planning system Treatment delivery system Precise targeting (stereotactic coordinate system) Patient positioning verification

Specialized Devices for SBRT
Novalis Cyberknife Accelerator-based IGRT (Trilogy, Synergy)

Essentials for SBRT
3-D Imaging device Treatment planning system Treatment delivery system Precise targeting (stereotactic coordinate system) Patient positioning verification

WFUBMC SBRT 3-D Imaging Device
Phillips PQ 5000 CT simulator Single slice acquisition External lasers for isocenter placement AcQSim software

WFUBMC SBRT “New” 3-D Imaging Device
GE Discovery ST CT/PET Simulator 8 slice, helical scan, LightSpeed (Ultra) CT scanner External lasers for isocenter placement Advantage Simulation Workstation software

WFUBMC SBRT Treatment Planning System
Phillips-ADAC 3D RTP system Accurate small field dosimetry Standard plan consists of 9 coplanar beams with negative margins

WFUBMC SBRT
Varian 2100 SCX accelerator 6MV photon beam 120 leaf MLC Portal Vision

WFUBMC SBRT Stereotactic Patient Positioning
Elekta Stereotactic bodyframe Cartesian coordinate fiducials Diaphragm breathing control Patient must pass “YMCA” test “Treat the box” approach

Stereotactic Patient Positioning
Precise targeting requires a stereotactic coordinate system or image-based targeting
Patient positioning verification is a MUST.

WFUBMC SBRT Patient Repositioning Verification
Elekta bodyframe lasers (2 chest points plus leg marker Serial CT image sets on day of simulation “GTV” is defined from the fusion of 2 image sets (i.e. “4-D GTV”)

WFUBMC SBRT Patient Repositioning Verification
On day of treatment SSD checks and orthogonal isocenter portal images Physician approval of isocenter images required before treatment proceeds. Total time on linac is about 1 to 1.5 hours

WFUBMC SBRT Orthogonal Portal Images

Fraction #1

Fraction #2

Fraction #3

WFUBMC SBRT Patient Positioning Verification
Neuro-surgical Stealth Station computer system Stereo IR camera Fiducials placed on SBF and patient System detects shifts in patient, relative to the SBF

WFUBMC SBRT Patient Positioning Verification
Patient No. 1 2 3 4 GTV Isocenter shift (mm)* 3.7 4.1 3.0 6.7 Stealth Station RMS Error (mm) 0.7 1.5 0.6 0.8

*Shifts mainly in axial direction on 3mm thick slices.

WFUBMC SBRT
Through March, 2005, 70 SBRT patients have been treated using the Elekta Bodyframe. Of these 70 patients, 30 patients have been treated in a single fraction on our Stereotactic Body Radiosurgery protocol. Others have received between 2 and 4 fractions.

WFUBMC SBRS PROTOCOL
CCCWFU 99502: “A Phase I/II Dose-Escalation/Efficacy Study of Palliative Extracranial Radiosurgery using the Elekta Stereotactic Body Frame System.”
Eligibility criteria:  The presence of a well-circumscribed tumor (primary or metastatic) on contrast-enhanced CT scan with a maximum diameter of 6 cm.  Age  18 years with a life expectancy  3 months.  No chemotherapy or immunotherapy were allowed at least 3 weeks prior to or planned for 4 weeks after treatment.

WFUBMC SBRS PROTOCOL
 Patients were stratified to dose levels by tumor volume  Phase I Endpoint: Acute toxicity using NCI Common Toxicity Criteria 3.0  Phase II Endpoint: Local control by CT RECIST Criteria (Response Evaluation Criteria In Solid Tumors)
Dose (Gy)
Tumor Volume Stratification Phase I Phase II Small < 25 cm3 15 → 22.5 → 32.4 13 → 22.5 Medium 25 cm3  65 cm3 12 → 18 → 28.5 10 → 18 → 22.5 Large 65 cm3 - 120 cm3 10 → 15 → 20 8 → 15 → 20

WFUBMC SBRS PROTOCOL
28 patients have been enrolled on study. 12 (43 %) of these patients have had PET imaging for a minimum of 3 months. We report the results of these patients. For the PET group, median follow-up so far is 377 days (171-739 days). Median survival has not yet been reached. 3 deaths have occurred. For these 3 patients, median survival from time of treatment was 250 days.

WFUBMC SBRS PROTOCOL
Local control at 3 months was 100 %. The median change in tumor diameter at 3 months was -14 % (-59% to 0 %) for a median RECIST of SD. The median corrected SUV change at 3 months was -57 % (-13% to + 11%).

WFUBMC SBRS PROTOCOL
 8 patients have had no progressive disease (PD).  For 7/8, the SUV decreased and had not increased by the last follow-up.  4 patients have had PD by RECIST.  3/4 had a corresponding rise in correct SUV, which preceded the RECIST progression by a median of 71 days (71-75 days).  The median time to RECIST failure for these patients was 238 days (175-319 days).  Overall, the correlation between RECIST control and PET control was 0.71.

WFUBMC SBRS PROTOCOL
In the acute phase (< 3 months), there appears to be no significant inflammatory response by PET. In the late phase, (> 3 months) PET progression appears to precede RECIST PD by 2.4 months. This may have implications for the timing of subsequent therapy (e.g. chemotherapy).

POSSIBLE IMPROVEMENTS
Respiratory gating On-board KV imaging Cone beam imaging

THANK YOU


				
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posted:4/24/2008
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