Comparison of Clinical Parameters for Proton Therapy in the United

States

Paige Summers, MS

Disclosure

•This project is supported by the Federal Share of program income earned by Massachusetts General Hospital on C06 CA059267, Proton Therapy Research and Treatment Center and by grants CA10953 and CA81647 (NCI, DHHS).

RPC Background

•Funded by the NCI, tasked with ensuring that radiotherapy institutions participating in clinical trials deliver clinically comparable and consistent doses

•Asked to develop monitoring program for proton therapy facilities too

Proton Therapy Facilities

• Monitored by RPC:

• 10 clinical sites

• 1 international site in Japan

• Forecast ~20 new centers

•Will likely see increase in clinical trials with proton therapy, making comparability important

NJ 2012

Shizuoka 2003

Proton Approval Steps

•Proton facility questionnaire

•Annual monitoring of beam calibrations by the RPC

•Ability to electronically transfer treatment plans

•Irradiation of RPC’s baseline proton phantoms

•On-site dosimetry review visit

Information Collected by the RPC

•Typical review components:

•Dosimetry equipment calibration

•CT scanner, CTN/RSP conversion

•Patient immobilization

•Treatment planning procedures

•QA documentation

Patient Simulation Parameters

Institution Scanner kVp mAs Slice Thickness Acquisition Mode Pitch SFOV [cm]

1 GE LightSpeed RT 16 140 600 1.25 mm Axial N/A 50

2 GE LightSpeed RT 16 120 300 2.5 mm Helical 0.94 50

3 Philips PET / Big Bore 120 / 140 500 / 400 1.25 mm Helical 0.51 / 0.56 65 / 85

4 GE VCT 120 350 2.5 mm Axial/Helical N/A / 0.94 50

5 Siemens Biograph 16 PET 120 / 140 150 1 mm Helical 0.55 50

6 Siemens Sensation 120 300 1.5 mm Helical 0.75 50

7 GE LightSpeed RT 16 140 250 1.25 mm Helical 0.94 50

8 GE LightSpeed RT 16 120 300 1.25 mm Helical 0.98 50

• Values obtained during on-site audit

• Can institutions improve simulation imaging parameters? Lower CT dose?

Treatment Margins•Described by institution in facility questionnaire

Site-Specific Lateral Margins [mm]Brain H&N Abdomen Pelvis

Institution 1 2.5 3 5 5

Institution 2 3 3 5 5

Institution 3 3 3 5 5 - 8

Institution 4 5 7 7 - 9 7

Institution 5 2 2 2 2

Institution 6 3 3 5 - 7 5 - 10

Institution 7 5 5 5 5

Institution 8 3 3 - 5 5 - 10 3 - 5

Institution 9 2 2 5 5

Institution 10 3 5 5 5

Institution 11 5 5 10 10

Penetration Uncertainty Margins

Institution 1 3%

Institution 2 3.5% + 3mm

Institution 3 1.50%

Institution 4 3.5% + 3mm

Institution 5 2 mm

Institution 6 3.5% + 3mm

Institution 7 1% + 1mm

Institution 8 1.5% + 1.5mm

Institution 9 -

Institution 10 1% + 1mm

Institution 11 3.5% + 3mm

Prescribing Dose

Prescription LevelsBrain H&N Thorax Abdomen Pelvis Extremities

Institution 1 95 - 98% 95 - 98% 95 - 98% 95 - 98% 95 - 98% 95 - 98%

Institution 2 95 - 98% - 95 - 98% 95 - 98% 97.5% -

Institution 3 95% 92% 95% 95% 95% 95%

Institution 4 100% 100% 100% 100% 100% 100%

Institution 5 100% 100% 100% 100% 100% 100%

Institution 6 98% 98% 98% 98% 98% 98%

Institution 7 95% 95% 95% 95% 95% 95%

Institution 8 98% 98% 98% 98% 98% 98%

Institution 9 95% 95% 95% 95% 95% 95%

Institution 10 95% 95% 95% 95% 95% 95%

Institution 11 95% 95% 95% 95% 95% 95%

• Institutions normalizing in different ways, to different levels

Significance

•Differences exits across centers

•Task groups focusing on QA, papers on outcomes – not many recommendations about clinical parameters - could use more recommendations from experienced proton centers

•Important to consider variation of dosimetric parameters in planning clinical trials – proton alone or mixed modality

Questions???

Proton Approval Steps

•Proton facility questionnaire

•Annual monitoring of beam calibrations by the RPC

•Ability to electronically transfer treatment plans

•Successful irradiation of RPC’s baseline proton phantoms

•Successful completion of on-site dosimetry review visit

Facility Questionnaire

•AAPM Proton Advisory group aids RPC & QARC in updating proton facility questionnaire

•Submitted to QARC via email or paper – copy sent to RPC

•Questions covered:

• Experiences in the clinic

• Dose calibration & verification

• Proton beam production & delivery

• Treatment Planning

• Immobilization

• Patient Alignment

• QA

RPC Proton Site Visits

•Typical site visit measurements

• Beam calibration comparison – RPC/Inst

• CAX lateral and depth dose profiles for reference and patient fields

• Scanning beam – less fields tested, more profiles obtained

• X-ray system measurements

• TLD measurements