ESTRO meets Asia 2024 - Abstract Book

S359

RTT – Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO meets Asia 2024

hypofractionated prostate cancer patients. Tech Innov Patient Support Radiat Oncol. 2021 Sep 4;19:41-45. doi: 10.1016/j.tipsro.2021.07.001. PMID: 34527818; PMCID: PMC8430426. Leong B, Padilla L. Impact of use of optical surface imaging on initial patient setup for stereotactic body radiotherapy treatments. J Appl Clin Med Phys. 2019 Dec;20(12):149-158. doi: 10.1002/acm2.12779. PMID: 31833639; PMCID: PMC6909112.

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Digital Poster

A study on 3 types of patient immobilisation gadgets with IGRT for extended-field gynaecological RT

Yan Ru Chia, Jeannie YiXin Lin

Department of Radiation Oncology, National Cancer Centre Singapore, Singapore, Singapore

Purpose/Objective:

Extended-field gynaecological RT is a treatment for gynaecological cancer primary and nearby lymphatic drainage, including para-aortic nodes(1, 2). Because treatment volumes are large, irradiation of critical OARs such as rectum, bladder and bone marrow(3) can result in significant gastrointestinal, genitourinary and haematologic toxicities (HT)(4). A high rate of acute HT is a limiting factor for such treatment. Thus, reducing doses to the bone marrow through proper patient immobilisation is imperative to safeguard treatment efficacy(5) with accurate RT delivery to the target volume while minimising toxicities(6, 7). Three different immobilisation, in-house-made Lung Gadget (LG), AIO with (AIOWS) and without shell (AIONS) were compared to determine while immobilisation gadget has the best setup reproducibility for patients undergoing extended-field gynaecological RT based on the 3-directional shifts applied on pre-treatment images.

Material/Methods:

A retrospective analysis was conducted on 12 patients who used 3 different immobilization gadgets during treatment: LG, AIOWS, and AIONS. A total of 72 pairs of orthogonal kV images and 12 CBCT scans were reviewed. 252 three-directional shifts in the left/right (Lt/Rt), anterior/posterior (Ant/Post), and superior/inferior (Sup/Inf) were collated. Within the course of RT, the patient's weight changes were expected to become more prominent at 4 specific time points (3, 8). Hence, images on day 1, day 4, mid-treatment, and the last week of RT were collected. These images were independently reviewed offline by 1 radiation therapist for intra-rater reliability and 3D shifts were collected. Statistical method of one-way ANOVA with post-hoc Tukey HSD was used to evaluate the results.

Results:

AIOWS has been shown to provide a setup with the least three-directional shifts by comparing the mean magnitude of shifts among the three immobilisation gadgets. From the results, there was a statistically significant difference (p=0.044) between AIOWS and AIONS in the Ant/Post direction with AIOWS having better ant/post stability. However, no difference was observed in the Ant/Post direction when comparing LG to AIOWS and AIONS. Therefore, it is difficult to conclude the extent of shell usage in improving setup reproducibility. Also, there was no difference between Lt/Rt (p=0.787)and Sup/Inf (p=0.117) values of the 3 groups observed. Overall, the results suggest that all 3 immobilisation gadgets performed similarly for patient setup reproducibility.