Radiation and Cancer Physics

SS 37 - Physics 11 - Online Imaging and Motion Management

264 - Kilovoltage Intrafraction Monitoring (KIM) Real-Time Tracking Improves Patient Dose Distributions: Interim Primary Hypothesis Results from the First 20 Patients on the TROG 15.01 Stereotactic Prostate Ablative Radiation Therapy SPARK Trial

Wednesday, October 24
11:00 AM - 11:10 AM
Location: Room 302

Kilovoltage Intrafraction Monitoring (KIM) Real-Time Tracking Improves Patient Dose Distributions: Interim Primary Hypothesis Results from the First 20 Patients on the TROG 15.01 Stereotactic Prostate Ablative Radiation Therapy SPARK Trial
E. A. Hewson1, D. T. Nguyen1, R. O'Brien1, P. R. Poulsen2, J. Booth1,3, R. Bromley3, J. Kipritidis3, T. Moodie4, P. Greer5, T. Eade3, A. Kneebone3, J. Martin6, A. Hayden4, G. Hruby3, P. Hunter6, L. Wilton6, S. L. Turner1,7, V. Gebski8, and P. Keall1; 1University of Sydney, Sydney, Australia, 2Aarhus University Hospital, Aarhus, Denmark, 3Royal North Shore Hospital, Sydney, Australia, 4Westmead Cancer Care Centre, Sydney, Australia, 5University of Newcastle, Newcastle, Australia, 6Calvary Mater Newcastle Hospital, Newcastle, Australia, 7Sydney West Cancer Network, Western Sydney Local Health Disctrict, Sydney, Australia, 8NHMRC Clinical Trials Centre, University of Sydney, Sydney, Australia

Purpose/Objective(s): Kilovoltage Intrafraction Monitoring (KIM) is an emerging real-time image guidance technology that allows real-time intrafraction motion monitoring on a standard linear accelerator. In the TROG 15.01 Stereotactic Prostate Ablative Radiotherapy with KIM (SPARK) trial, KIM was used to enable real-time image guidance in a multi-institutional setting. We performed a planned 20-patient interim analysis of the SPARK trial data to test the primary hypothesis that KIM improves patient dose distributions.

Materials/Methods: Twenty men with prostate cancer were treated with KIM-guided SBRT delivering 36.25 Gy to the PTV in 5 fractions at three institutions. During treatment the target motion was corrected in real-time by implementing beam gating and couch shifts (55 fractions) or multileaf collimator tracking (45 fractions). A time-resolved motion encoded dose reconstruction method was used to retrospectively evaluate the delivered dose distribution to the target and organs at risk and compare to what would have been delivered without real-time image guidance. Simon’s two-stage design with 90% power and 95% confidence was used to rule in a KIM success rate of 2/3 in favour of the futile rate of 1/3.

Results: KIM was used successfully in 98 of the 100 fractions. Intrafraction interventions were required in 66% of the successful fractions. The proportion of motion-corrected fractions with an improvement in dose distribution to both the prostate and rectum was 88% (57/65 fractions), significantly higher than the expected success rate of 67% (p<0.01, χ2). We accept the hypothesis that KIM improves patient dose distributions. Without KIM, only 65% of motion-corrected fractions would have received a dose coverage within 5% of the PTV prescription. With KIM, 100% of fractions achieved a dose coverage within 5% of the PTV prescription. With KIM, the dose delivered to the bladder and rectum were maintained within 4% of the planned values in all fractions. Without KIM, the bladder and rectum would have been overdosed in 25% and 6% of fractions, respectively. Detailed analyses are presented in the attached table.

Conclusion: The interim analysis showed that KIM is clinically useful in improving the prostate and rectum dose in the presence of intrafraction motion, allowing prostate patients to benefit from SBRT. The successful use of KIM in the SPARK prostate cancer trial provides a pathway for the wide adoption of real-time image guidance on modern linear accelerators, advancing the standard of care worldwide.
Percentage of fractions with intervention CTV D98 (%) PTV D95 (%) Bladder V70 (%) Rectum V70 (%)
With KIM Without KIM With KIM Without KIM With KIM Without KIM With KIM Without KIM
Exceeds 3% of plan value 3 25 2 48 2 25 2 6
Exceeds 5% of plan value 0 12 0 35 0 14 0 2

Author Disclosure: E.A. Hewson: None. D. Nguyen: None. R. O'Brien: Founder, shareholder; Opus Medical. P.R. Poulsen: Research Grant; Varian Medical Systems. J. Booth: Research Grant; NHMRC, Varian Medical Systems, Cancer Australia. R. Bromley: None. J. Kipritidis: None. P. Greer: Employee; Calvary Mater Newcastle. Research Grant; Radiation Oncology Institute, Varian Medical Systems. Task Group Committee 264; American Association of Physicists in Medicine. Task Group Committee 307; Amereican Association of Physicists in Medicine. T. Eade: None. G. Hruby: None. P. Keall: Research Grant; Philips Medical, US NCI/NIH, Australian NHMRC, Australian Research Council, Varian, Cancer Australia, Australian Cancer Research Foundation, Prostate Cancer Foundation of Australia. Co-Investigator (PI Booth) for equipment and support for MLC tracking and KIM; Varian. In-kind Donation; Philips Medical. Stock; Respiratory Innovations, Nano X Pty Ltd, SeeTreat Pty Ltd. Partnership; Cancer Research Innovations. Royalty; Varian Medical Systems, Standard Imaging. Various; AAPM, ACPSEM, Journals.

Jeremy Booth, PhD

Disclosure:
Employment
Royal North Shore Hospital: Chief of Medical Physics: Employee

Compensation
Cancer Australia: Research Grants; NHMRC: Research Grants; Varian Medical Systems: Research Grants

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264 - Kilovoltage Intrafraction Monitoring (KIM) Real-Time Tracking Improves Patient Dose Distributions: Interim Primary Hypothesis Results from the First 20 Patients on the TROG 15.01 Stereotactic Prostate Ablative Radiation Therapy SPARK Trial



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