Room: Track 2
Increasing interest in stereotactic ablative radiotherapy (SABR) has boosted the need for real-time image-guided radiotherapy (IGRT). Kilovoltage Intrafraction Monitoring (KIM) is an image-guidance technology that utilizes the on-board kV imager on a linac to achieve real-time motion monitoring. This study reported the total dose improvement received by patients treated in the TROG15.01 Stereotactic Prostate Ablative Radiotherapy with KIM (SPARK) trial.
Forty-four prostate cancer patients were treated across four institutions using KIM-guided SABR with 36.25Gy prescribed to the PTV. Prostate motion was monitored using KIM and corrected in real-time using gating and couch-shifts (34 patients) or MLC tracking (10 patients). The dose delivered to the prostate and organs at risk was retrospectively evaluated using a motion-encoded dose-reconstruction method and compared to an estimation of what would have been delivered without real-time IGRT.
39/44 (89%) patients had at least one fraction where motion was corrected. The patient dose over five fractions showed that all patients treated with real-time IGRT received a dose within 5% of the planned PTV D95%. Without real-time IGRT, six patients (14%) would not have received a dose within 5% of the planned PTV D95%. When real-time IGRT was used, the range of differences between the plan and delivered doses for the CTV D98%, PTV D95%, rectum V30Gy, and bladder V30Gy were [-0.9%, 1.1%], [-2.3%, -0.8%], [-1.8%, 1.4%] and [-1.4%, 1.7%] respectively. If patients were treated without real-time IGRT the range of differences would have been [-5.6%, 1.1%], [-17.0%, 0.8%], [-6.2%, 1.2%] and [-2.9%, 8.5%] respectively.
For the first time, the total dose delivered over a SABR course for prostate cancer patients treated using KIM-guidance was quantified. Without real-time IGRT, the dose to the targets of 14% of the trial cohort would be compromised, further emphasizing the importance of real-time IGRT for high dose treatments.
Funding Support, Disclosures, and Conflict of Interest: The authors acknowledge funding from Cancer Australia. PJK is an inventor of licensed and unlicensed patents related to the KIM technology.