Jean Pouliot, PhD Professor and Vice Chair, Department of Radiation Oncology, Director of Physics Division

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1 IMRT / Tomo / VMAT / Cyberknife / HDR Brachytherapy: Jean Pouliot, PhD Professor and Vice Chair, Department of Radiation Oncology, Director of Physics Division Should Choices be Based on Dosimetric and Motion Considerations? UC-Berkeley - UCSF Graduate Program in Bioengineering Genitourinary Cancers Session, March 22nd,

2 Disclosure Industrial Research Contracts Accuray, Dosisoft, Philips, Siemens, Varian Grants UC-Proof of Concept 12-PC-247 UCSF CTSI Catalyst Award 2014 Licensing Agreement Nucletron/Elekta 2

3 Collaborators Josephine Chen, PhD Adam Cunha, PhD Martina Descovich, PhD Aaron Garcia, MS Alex Gottschalk, MD I-Chow Hsu, MD Dilini Pinnaduwage, PhD Mack Roach, MD 3

4 Educational Objectives IMRT - VMAT - TOMO - CK - HDR - Understand that each modality follows a paradigm - Understand when motion management is required

5 Dose Distributions Ck Tomo GammaK

6 Dose Distributions HDR Tomo Ck GammaK

7 Dose Distributions

8 Dose Profiles HDR Brachy

9 DOSIMETRIC COMPARISON IMRT - VMAT - TOMO - CK - HDR - 3 Patients (prostate volumes: 35, 36 & 40 cc) - Prostate, bladder, rectum, bladder, and urethra - All structures segmented by same physician - Specific clinical planning team for each modality was asked to plan as usual. - Prostate only - No consideration of RBE

10 Average Dose Comparison TOMO IMRT VMAT CK HDR Brachytherapy Average Dose to Target for a Constant D95 103% 104% 105% 116% 147% Falloff (V100/V50) Urethra V120%(cc)

11 HDR Brachytherapy: RTOG0321 Acute adverse event... the dose-limiting structure for prostate HDR brachytherapy is in the target volume (urethra). Late adverse event This is in contrast to external beam radiation therapy where the rectum is the dose-limiting structure. Percent Dose of Prescription Dose

12 Urethra-sparing dose distribution

13 CK Urethra Sparing Objective: Mean urethra dose < Prescription

14 UCSF Protocol for Prostate Robotic - SBRT - 3 gold fiducial markers in prostate - T1 and T2-weighted MRI (T1 for markers, T2 for urethra and prostate) - Planning CT (1.5mm) and T2-weighted MRI are co-registered - PTV = Prostate + 2mm expansion* (except posteriorly) - OAR: Bladder, rectum, urethra, penis, testicles, bowel & femoral heads - Field sizes (Iris) ranging from largest aperture that fits the PTV contour to 12.5 mm-diameter opening are selected. - Maximum of 200 MU per beam per fraction - Four asymmetric shells are created around the PTV * due to intrafraction motion

15 Intra-fraction Prostate Motion Study: 2438 alignment shifts/rotations during Y fractions for 13 consecutive prostate patients, with a 90 sec average time between image verifications. - PTV Margin of 2mm - Time between images < 60 sec

16 Evidence-based dose constraints for prostate Ck-SBRT Dose Planning Problematic: Difficult to predict level of OAR protection -> plan might not be optimal Objective: Use anatomy to determine possible level of sparing Favorable Unfavorable

17 Evidence-based dose constraints for prostate Ck-SBRT - Dose limits depend on anatomy - Expansion-Interception-Volume (EIV) EIV = intersection volume between the target and the organ at risk expanded by 5 mm.

18 Evidence-based dose constraints for prostate Ck-SBRT - EIV vs V75 - Clinical Use nci<1.25 nci 1.25 Descovich et al., Improving plan quality and consistency by standardization of dose constraints in prostate cancer patients undergoing stereotactic body radiation therapy, JACMP 2014 (In Press).

19 Tomotherapy Fixed Jaw TomoEdge Supperior Inferior

20 TOMO / IMRT / VMAT / CK / HDR TOMO IMRT VMAT Target coverage and urethra protection insured by IGRT and dose uniformity CK HDR Urethra defined on MRI and intrafraction motion compensated via tracking Urethra (defined via Foley) sparing via dose tunnel

21 TOMO / IMRT / VMAT / CK / HDR TOMO Most uniform dose of linac IMRT techniques IMRT Most clinical experience VMAT Efficient way to deliver radiation, more than one arc needed. CK Hypofractionated Tx, intra-fx tracking, ~long Tx time HDR One-fx Tx, long clinical experience, caution with catheter motion

22 Thank You! Questions? Genitourinary Cancers Session, March 22nd,