Multi-target Tracking in Prostate Radiotherapy Using MLC and KIM

Phase I Feasibility Study of Accounting for Relative Motion of Multiple Targets in Prostate Cancer Radiotherapy Using Realtime Multi-leaf Collimator Adaptation and Kilovoltage (kV) Intrafraction Monitoring

Assessing the feasibility of implementing real-time multi-leaf collimator (MLC) tracking to account for the relative motion of the moving prostate tumour target and the static pelvic nodal target for high-risk prostate cancer patients. The capability of tracking for the relative motion of multiple targets will ensure that all the treatment targets receive correct dose as prescribed by the doctor and minimise side effects to the critical organs.

This study will assess the feasibility of implementing real-time multi-leaf collimator (MLC) tracking to account for the relative motion of the moving prostate tumour target and the static pelvic nodal target for high-risk prostate cancer patients. The capability of tracking for the relative motion of multiple targets will ensure that all the treatment targets receive correct dose as prescribed by the doctor and minimising side effects to the critical organs.

During radiation treatment, the prostate position will be monitored in real time using the KIM technology. The nodal target will be imaged before and after each treatment to evaluate the nodal treatment margin. The MLC tracking is implemented by recalculating the radiation beam shape fit for the moved prostate and static nodal targets and sending the adjusted MLC leaf positions to the treatment delivery system. The actually delivered dose to the patient will be calculated after the treatment and compared to the dose without MLC tracking to assess the treatment efficacy.

Inclusion Criteria:

• Patients undergoing definitive external beam radiotherapy at Northern Sydney Cancer Centre
• Patients histologically proven prostate adenocarcinoma
• PSA obtained within 3 months prior to enrolment
• Pelvic lymph nodes are included for treatment for patients at stage T1c-T3b with Gleason 8-10 or prostate-specific antigen (PSA) > 20 ng/ml or pelvic lymph node positivity on conventional imaging or prostate-specific membrane antigen (PSMA) scans.
• Patient must be able to have gold fiducial markers placed in the prostate
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Ability to understand and the willingness to sign a written informed consent document.
• Prostate dimension that allows leaf span with tracking margin of ±8mm

Exclusion Criteria:

• Patients with artificial Hip(s), lumbar spinal surgical rods or other large metallic pelvic implants
• Patient's dimensions >40cm as measured at the level of the prostate
• Patients with overlapping implanted gold fiducials in x-ray imaging