1. Vice President and Chief Medical Physicist
Recent Advances in Clinical Proton Beam Therapy - Exploiting the Benefits of Pencil Beam Scanning
Niek Schreuder
Vice President and Chief Medical Physicist
Provision Health Care

2. OUTLINE Classical Proton Radiation Therapy Proton Pencil Beam Scanning
Clinical Indications for Proton Therapy
The Future of Proton Therapy

3. The Goal of Radiation Therapy for 100 years:=
Tumor Control
Normal Tissue Complications
Therapeutic Ratio
Potential improvement in quality of life
Cost savings by decreasing complications
TR is defined as the balance between probability of tumor control and risk of normal tissue complications
It will be increased if tumor dose escalation can improve local control and/or normal tissue dose can be decreased to lower the risk of complications

4. Depth Dose Curves for Different Treatment Modalities
The Physics of Protons
Depth Dose Curves for Different Treatment Modalities
8 MV X-Rays
SSD = 100 cm
100
Depth of
Tumor
5 cm SOBP 80 60
Relative Dose
200 MeV Proton
Pristine Bragg Peak 40
Chris
The Chris / IBA rap
The improved dose distributions of protons, as compared to x-rays, allows increased dose delivered to the target volume, translating into improved local control.
Reduced dose to non-involved organs and tissues translates into reduced treatment morbidity and improved quality of life; reduced co-morbidity of multi-modality treatments, leading to improved treatment intensity and compliance.
Improved local control of malignancies translates into increased probability of survival for a significant proportion of patients. 20 5 10 15 20 25 30
Depth in Tissue (cm)
Protons 101

5. Radiation Therapy
Classical Proton Therapy

6. Scattered Beam Proton Therapy
Patient Contour
Target Area
Compensator
Inhomogeneity
(Air Pocket)
Aperture

7. PENCIL BEAM SCANNING – PBS
Pencil beam scanning (PBS) is the generic name for delivering the dose to a target using individually controlled small pencil beams to cover the target in 3 dimensions.

8. PENCIL BEAM SCANNING – PBS
The proton beam is actually not “pencil thin”
-A better size representation is actually a white board marker
PBS spot size (FWHM)

9. Pencil Beam Scanning (PBS) – Filling the target with spheres of Radiation dose

10. Advantage of Pencil Beam scanning
PBS offers Proximal and distal beam shaping
Dose outside the target (integral dose) is reduced significantly
Reduction of integral dose even more significant for large targets
Double scattering / Uniform Scanning
Dose Difference DS/US – PBS dose
Pencil Beam scanning

11. Proton Radiation Therapy
Classical Proton Therapy  DS/US + Single Field Optimization (SFO)
Pencil Beam Scanning –
Multi Field Optimization (MFO)

12. Clinical Realization of PBS Pencil Beam Scanning changed the landscape
Large non-contiguous
targets
Smaller contiguous
targets
Classic indications:
Base of skull tumors
Eye (uveal) melanomas
Brain tumors
Pediatric tumors
Spinal / Para spinal tumors
Prostate cancers
Lung
20 – 30 % of all radiation treatments
Pencil Beam Scanning changed the landscape
Lung
Liver
Breast
Esophagus
Pelvic tumors
Large sarcomas
High risk Prostate
Mediastinal tumors
Re-irradiation of recurrent tumors
80 % of all radiation treatments

13. Proton therapy  Projected Utilization of Protons
Prevention of complications
Improvement of local control
Prevention of secondary tumours
Main clinical use PREVENTION:
Complications
Secondary tumors
Standard indications
This is what protons have been used for before PBS became a clinical reality
Source: Horizon scanning report (Health council of the Netherlands 2009)
With Compliments – Dr Hans Langendijk - UMCG

14. Robust Optimization  the “certainty” of proton dose delivery
(a) Nominal setup
(b) Shifted setup
Evaluate the uncertainties in the dose delivered by a single spot +
Give higher weights to those spots with less uncertainty
Instead of setting margins – specify uncertainties – no need for a PTV
Robust optimization is also referred to as “Inverse planning of Margins”

15. Sphere of confusion = 2mm diameter
Set-up Tolerances
Sphere of confusion = 2mm diameter
Up to 1 mm – cannot conclude anything
Typical setup threshold
Typical Plan Design margin
Robust optimization Parameters
1 mm
2 mm
3 mm

18. 2 Field CSI to 23.4 CGE METHODS Field Size 30 x 40 cm 2 Fields only
Junction Length = 10 cm
Gradient = 1.1% per 1mm
Robust Optimization to Brain
Range Uncertainty 2.5% + 1mm
Treatment Time ~ minutes

19. 2 Field CSI to 23.4 CGE
Skin dose ~ 85%

20. Pelvic Lymph Node Treatment High Risk Prostate Cancer
Left lateral field
Right lateral field
Combined fields
Maximum sparing of:
Bladder
Small bowel
Rectum

21. Stenosis of the main coronary artery left anterior descending (LAD)
Coronary Exposure to Radiation in Conventional Radiotherapy for Breast Cancer
Stenosis of the main coronary artery left anterior descending (LAD)

22. Use Protons
Spare the heart
and coronaries

23. Breast Cancer – Protons vs. Conventional Radiotherapy
Photons / Electrons
Protons
RCA
LAD, D-1, D-2
Photons minus protons = excess dose
Potential Impact:
Coronary artery stenosis
Second Malignancy
Lung function

24. Medium Intact Breast Dashed – Photons (X-Rays) Solid - Protons Skin
IRRADIATED VOLUME 
Left Lung
LAD
DELIVERED DOSE 

25. Clinical Realization of PBS Pencil Beam Scanning changed the landscape
Large non-contiguous
targets
Smaller contiguous
targets
Classic indications:
Base of skull tumors
Eye (uveal) melanomas
Brain tumors
Pediatric tumors
Spinal / Para spinal tumors
Prostate cancers
Lung
20 – 30 % of all radiation treatments
Pencil Beam Scanning changed the landscape
Lung
Liver
Breast
Esophagus
Pelvic tumors
Large sarcomas
High risk Prostate
Mediastinal tumors
Re-irradiation of recurrent tumors
80 % of all radiation treatments

26. NEW TECHNOLOGY – Reduce Size
Conventional 360
Gantry
PRONOVA
SC 360

27. Accelerator Evolution
F2800
Ironless variable energy
SC synchrocyclotron
(no degrader necessary)
MIT – ProNova Collaboration
ProNova Development
Sumitomo - ProNova Collaboration

28. U.S. Proton Therapy Centers
1 Massachusetts General Hospital, Boston
2 Loma Linda University Medical Center, Calif. 
3 MD Anderson Cancer Center, Houston (PTCH)
4 University of Florida Proton Therapy Institute,
5 ProCure Proton Therapy Center Oklahoma City,
6 University of Pennsylvania Health System, Philadelphia
7 Hampton University Proton Therapy Institute, Hampton
8 ProCure Proton Center, Chicago
9 ProCure Proton Center, New Jersey
10 ProCure Proton Therapy Center, Seattle
11 Washington University, St. Louis
12 Provision Center for Proton Therapy, Knoxville
13 Scripps Proton Therapy, San Diego
14 Willis Knight Shreveport LA
Ackerman Cancer Center, Jacksonville
Mayo Clinic – Rochester MN
Robert Wood Johnson, NJ
Texas Oncology, TX
St Jude’s, TN
Maryland
In Operation (22)
10 sites currently operating in the US.
32 by June 2018
Under Construction (10)
Under Development (20 or ?)

29. How can more people get access to Protons?
Equipment costs are coming down + project time lines are decreasing rapidly  time = money
Virtual Proton Centers – Interim Solution
Participate in a network of existing proton centers
PCPT is an open center
Other physicians / Physician groups can participate through a credentialing process
The Virtual Proton Center will
Perform the consult
Develop the care plan
Conduct the CT scan + other imaging required
Create the treatment plan
Proton therapy treatments would then occur at PCPT
Follow-up will be at the virtual proton facility

30. Conclusions
Protons – employing pencil beam scanning - will have the largest impact in large distributed targets
The next steps in technology advancements will make protons much more affordable and available
PBS changed the radiation therapy landscape over the past 3 years and PBS is the future of Proton therapy
The only problem with protons is “the lack of protons”

31. Thank You