ESTRO 2024 - Abstract Book

S5915

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

3. RTP imaging includes an empty bladder CT, a full bladder CT with IV contrast and an RTP MRI including small field of view (FOV) T2 axial and sagittal sequences, together with a large FOV dixon sequence to encompass the pelvic and para-aortic lymph nodes. MRI is acquired with a mid bladder volume in a dedicated 30-minute RTP slot. Rectal AP diameter is limited to 4.5cm.

4. Target localisation is performed in keeping with EMBRACE 2 protocol which is our standard of care.

5. 3 PTVs are created reflecting tumour and elective nodal target volume at full, mid and empty bladder volumes. These are called PTV1, PTV2 and PTV3, respectively. A 4th back up PTV encompasses all of these volumes (PTV_Combi), voluming of additional structures takes no more than 30 minutes of clinician time. 6. Planning created a template in Eclipse with contours required, taking 15 minutes to create. The planning took 2-2.5 hours for each plan. Checking the plans took 2 hours each. Because of increase physics time required, we are limited to planning 1 patient with POTD for cervix cancer a week. 7. RTT training database, workbook and competency assessment for plan selection were created which took a month. 25 CBCT’s within the database were assessed by the clinician and 3 Senior Radiographers independently. The results collated were discussed and a gold standard answer set. RTTs were trained utilising the workbook and reviewed the CBCTs in the database and answered which plan they would select for each one. When they passed, online training was provided where they had to image and select the appropriate plan for 5 sessions. 12 senior radiographers have received the training to date. 8. The plan selection pathway requires the RTT to acquire the CBCT, perform image registration with a bone match and review the position of the cervix and uterus by selecting each PTV individually. The most suitable PTV for the position of the volume on the day is selected. The corrections are applied, the patient is closed on the linac and RTT 2 then selects and schedules the plan with the corresponding PTV and treatment is delivered. 9. An optimised pelvis CBCT is acquired and the time slots allocated for treatment are currently 45 minutes to avoid unnecessary pressures. All CBCT’s are reviewed by 2 RTT’s independently online and undergo an MDT offline weekly review.

Conclusion:

1. Workflow set-up for implementation took a year.

2. Implementation per patient required additional time, 30 minutes for clinicians, 13.5 hours for physics, and 2 hours for RTTs. We anticipate that the additional time required will reduced significantly with experience and confidence with this new technique. Early results already show that the treatment slots are generous. 3. POTD is beneficial to the patients as we are selecting a plan tailored to the patient which will minimise side effects from the radiotherapy and improve the patient experience as they did not have to come off the bed to further fill or empty their bladders, reducing their time in the department. Early results show the need to use all three plans.

Keywords: Cervix, Adaptive, POTD