ESTRO 2023 - Abstract Book

S2106

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ESTRO 2023

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. 1 ACTREC, Tata Memorial Center, Radiation Oncology, Navi Mumbai, India; 2 ACTREC, Tata Memorial Center, Medical Physics, Navi Mumbai, India; 3 Tata Memorial Hospital, Radiation Oncology, Mumbai, India; 4 Tata Memorial Center, Radiation Oncology, Mumbai, India Purpose or Objective To compare the contours of organs at risk (OAR) by radiation therapy technologist (RTT) and radiation oncologist in training/residents (ROr) for rectal cancer patients. Materials and Methods The RTT (PN, RT) and ROr (SM) were trained to contour OARs (bladder, bowel, left and right femur) as per the national rectal cancer guideline, UK, 2021. Both groups contoured each OAR for 28 patients independently on planning CTs of previously treated rectal cancer patients. The volume and the dimensions (length, width, depth) in the plane of the largest dimension in the 3D view on the planning system were documented for each of the OAR of by RTT and ROr respectively. The two sets were reviewed by a senior radiation oncologist (Ros; SG, RK, RE) for visual acceptability. The mean volumes and other dimensions for each OAR in the two sets were compared using analysis of variance (ANOVA) where p-value < 0.05 were considered statistically significant. Results All contours of OAR for RTT and ROr were found appropriate by each of the Ros independently. There was no significant difference in mean SD volume determined by ROr versus (Vs.) RTT for bladder, small bowel, left femur and right femur [355.39 ±169.22 Vs. 356.28 ±169.29cc (p=0.98), 953.15 ±346.55 vs 973.31 ±363.15cc (p= 0.83), 110.73 ±25.99 vs. 111.52 ±25.93cc (p=0.86) and 111.97 ±25.60 vs 112.32 ±25.58 cc (p=0.84) respectively]. Similarly, the maximum length, width and depth dimensions determined for bladder (p=0.88, 0.98 and 0.99 respectively), small bowel (p=0.97, 0.82 and 0.84 respectively), left femur (p=0.31, 0.90 and 0.94 respectively) and right femur (p=0.89, 0.84 and 0.93 respectively) were not significantly different between RTT and ROr. Conclusion There was a good concordance observed for the contouring of common OARs for rectal cancer among RTT and ROr after training. This can help in busy centres to help in role and responsibility distribution. With refinement and standardization of auto-contouring tools for common OARs, role of RTT may be explored for allowing routine evaluation, editing and approval of auto-contours for common OARs. PO-2340 The emerging role of radiation therapists in contouring organs at risk for rectal cancer. P. Negi 1 , R. Thigle 1 , J. Jain 2 , S. Mani 3 , S. Gudi 4 , R. Krishnatry 4 , R. Engineer 4

PO-2341 Adjuvant Hypofractionated SIB Radiotherapy: Retrospective study of dosimetry features

A. Martins 1

1 Fundação Champalimaud, Radiotherapy, Lisbon, Portugal

Purpose or Objective Purpose: Hypofractionated with simultaneous integrated boost radiotherapy (HFSIB) improvements in dosimetry features are refining radiotherapy treatment for patients (PTS) with early breast cancer (EBC) receiving whole breast adjuvant radiotherapy after breast-conserving surgery (WBRT-BCS). Non-inferior local control; toxicity; boost dose/schedule and tumour biology outcomes are emerging in literature. Materials and Methods Methods: A retrospective descriptive dosimetry study with PTS who underwent adjuvant HFSIB WBRT-BCS. EBC PTS enrolled with CDIS and invasive carcinoma. Bilateral and Nodal RT were exclude. Systemic treatment was neoadjuvant or adjuvant with anti-HER2+, hormonal therapy and BTA has recommended. HFSIB dose/schedule was whole breast 40.5Gy with 48Gy to tumour bed /15F, daily fractions of 2.5 Gy [EQD2/BED α / β 3 46.2/77.0Gy – α / β 10 52.9/51.4Gy] and 3.2 Gy [EQD2/BED α / β 3 59.5/99.2Gy – α / β 10 52.8/63.4Gy], respectively. Treatment techniques were intensity-modulated radiotherapy and volumetric modulated arc therapy (IMRT/VMAT), with Monaco TPS multicriteria optimization. We assessed dosimetry