Analysing the feasibility of adapted MR-guided SABR for prostate cancer patients with hip prosthesis
Addalin Huynh,
United Kingdom
PO-2339
Abstract
Analysing the feasibility of adapted MR-guided SABR for prostate cancer patients with hip prosthesis
Authors: Addalin Huynh1, Ami Sabharwal2, Ben George3, Ebison Chinherende4, Derya Yucel5, Daniel Murray6, Philip Camilleri2, Hannah Harford-Wright7, Joseph Drabble7, Peter Maungewe7
1GenesisCare , MR- Linac Senior Radiation Therapist, Oxfordshire, United Kingdom; 2GenesisCare, MR-Linac Radiation Oncologist, Oxfordshire, United Kingdom; 3GenesisCare, MR-Linac Lead Physicist, Oxfordshire, United Kingdom; 4GenesisCare, MR-Linac Senior Dosimetrist, Maidstone, United Kingdom; 5GenesisCare, MR-Linac Lead Physicist, London, United Kingdom; 6GenesisCare, MR-Linac Senior Dosimetrist, London, United Kingdom; 7GenesisCare, MR-Linac Senior Dosimetrist, Oxfordshire, United Kingdom
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Purpose or Objective
In the presence of metal hip prosthesis, CT-based planning images and CT-guided treatment images contain considerable image artefacts. This can limit the ability to delineate the treatment target and perform on-line imaging matching, making planning and delivery of ultra- hypo-fractionated prostate radiotherapy infeasible for these patients.
In contrast, MR images acquired for planning as part of the daily adaptive workflow in MR-guided radiotherapy (MRgRT) provides significantly improved characteristics, allowing for confident target visualization, image matching and real-time imaging during treatment. Through this improved anatomical visualisation and delineation, ultra hypo-fractionated treatment is considered feasible in these patients.
In this retrospective study we review the accuracy, quality, safety, and outcomes of daily adaptive MR-guided ultra-hypofractionated prostate radiotherapy in patients with uni- or bilateral hip prosthesis.
Material and Methods
Patients treated with daily adaptive MRgRT to their prostate ± seminal vesicles with doses of 36.25 in 5# with an optional 40 Gy boost to the prostate and proximal 1 cm of seminal vesicles for high-risk patients were eligible for inclusion.
Treatment accuracy was confirmed by reviewing the impact of metal hip prosthesis on image spatial integrity measured with a 2D distortion phantom.
Dosimetric play quality was compared between patients with and without hip prosthesis. Key metric included: volume of the PTV receiving the 100% and 95% of the prescription dose (PTV: V(100%), V(95%)), prescription dose spillage (PDS) and modified gradient index (MGI).
Patient reported toxicity data and PSA levels were used to assess safety and outcomes from these patients.
Results
We have planned 212 patients of MRgRT prostate cancer (PCa), including 10 with metal hip prosthesis.
The prostate volumes for the patients with metal hip prosthesis were 40.97-118.24 cc. Dosimetry for these patients for baseline plans were similar to treatments planned for those without metal hip prosthesis whilst meeting OAR dose constraints and achieving optimal PTV coverage. There was no statistically significant difference in PTV V(100%) and PDS between patients with and without hip prosthesis; p value of > 0.05. Toxicities and PSA levels for these patients post follow up period were clinically acceptable and minimal.
Conclusion
Results from our adaptive MRgRT SABR prostates with metal hip prosthesis shows that considerable metal artefact reduction with MRgRT allows for better visualisation and target/OARs delineation. Therefore, demonstrating an increased accuracy and efficacy in planning and treatment whilst minimising dose to OARs. Confidence in delivering MRgRT SABR treatment for this group allows us to provide quality treatment outcomes for this aging population with increased hip replacements.