ESTRO 2023 - Abstract Book

S2022

Digital Posters

ESTRO 2023

In current study both IGRT workflows showed excellent improvement in pelvic patient positioning using SGRT compared to the tattoos-based setup. In addition, patient roll and yaw have been improved using the SGRT setup. So, pelvic patients can undergo daily SGRT-based setup for accurate and reproducible patient positioning without additional imaging dose.

PO-2248 Patient positioning accuracy with surface guided radiotherapy

D. Mychko 1 , P. Dziameshka 2 , A. Zverava 1 , S. Siamkousky 1 , N. Shautsou 1 , M. Chyrets 1

1 Minsk City Clinical Oncologic Centre, Radiotherapy Department, Minsk, Belarus; 2 N.N. Alexandrov National Cancer Centre of Belarus, Laboratory of radiotherapy, Lesnoy, Belarus Purpose or Objective The study aims to evaluate the patient’s positioning accuracy for surface guided radiotherapy (SGRT) as well as to compare the positioning reproducibility for SGRT and the standard laser-based setup radiotherapy (LSRT) using free-breathing (FB) and deep inspiration breath-hold (DIBH) techniques. Materials and Methods 152 patients were enrolled in the study. 74 patients received LSRT using thermoplastic masks for breast cancer and skin markers for pelvic cancer RT. 78 patients underwent SGRT, thermoplastic masks or skin markers were not used. 44 patients (21 LSRT and 23 SGRT patients) received DIBH RT. Positioning accuracy for LSRT and SGRT was quantified with cone-beam CT (CBCT) in general cohort and the groups regarding the region of irradiation and the technique. 5 mm isocenter displacement and 3° rotation for transverse (Ox), longitudinal (Oy) and vertical (Oz) axes were considered to be acceptable. 897 CBCTs were performed. Mann-Whitney test was conducted on comparisons (p <0.05). Results Statistical analysis revealed no significant differences between LSRT and SGRT in the values of deviation from the reference point along the Ox, Oy, Oz axes in the general cohort and groups regarding the region of irradiation (p >0.05). A statistically significant advantage of LSRT over SGRT was revealed in terms of rotation control for pelvic RT – the medians of the Oz rotation angle for SGRT and LSRT were -0.8°(-1.6°; 0.4°) and 0°(-0.8°; 0.7°), p=0.02, the medians of the Ox rotation angle – 0.9°(-0.3°; 2.5°) and 0,2°(-1.1°; 1.2°), p = 0.003, respectively. A statistically significant advantage of SGRT over LSRT was revealed for DIBH patients – the medians of the displacement along the Ox axis were 0.1(-2.2; 2.8) and -1.1(-3.2; 2.2) mm, p=0.032 respectively (Table 1). Table 1. – Medians of reference position deviation for compared techniques

The deviations to be obtained did not exceed the valid values, therefore LSRT and SGRT were recognized as clinically equal.

Conclusion SGRT showed high efficiency regarding accuracy of patient set up and positioning control. It makes possible to reduce the thermoplastic masks and skin markers usage without compromising RT accuracy and minimize the limitations for DIBH application.

PO-2249 Is photo biomodulation effective in managing oral mucositis in head and neck radiotherapy?

E. Smith 1 , V. Poole 2 , E. Casey 3