ESTRO 2022 - Abstract Book

S589

Abstract book

ESTRO 2022

PD-0654 Surface Guided Radiotherapy accuracy vs tattoos position in 5- fractions breast radiotherapy.

D. gonsalves 1 , J. Fernandez 2 , A. Seral 2 , J.I. Sanchez 3 , E. Luguera 3 , I. Pajaro 4 , A. Parra 4 , C. Ferrer 4 , L. López 4 , S. López 4 , A. Carreras 4 , E. López 1 1 Genesis Care, Radiation Oncology, Madrid, Spain; 2 GenesisCare, Radiation Oncology, Barcelona, Spain; 3 GenesisCare, Radiation Physics, Barcelona, Spain; 4 GenesisCare, Radiotherapy Technologists , Barcelona, Spain Purpose or Objective The aim of this study is to compare the accuracy in set up position between SGRT and Tattoo-based method in 5 fractions adjuvant breast radiotherapy. Materials and Methods 60 patients were selected for the study and divided equally in two groups: a tattoo-based method group and SGRT group. The first group received 4 dark ink tattoos. The first tattoo was anterior and midline in the chest. The second and third laterally on the right and left side of the chest and the four 4 cm above the first one . The patient was positioned aligning the tattoos with the laser localisation then shift were made to move to the isocentre. The SGRT group was determined by AlignRT® system that tracks the patient’s skin surface in real-time with a pre determine region of interest (ROI). The ROI in this group included the isocentre, breast tissue and a stable surface such as mid -sternum and upper ribs. In SGRT, the left sided breast patients were treated with deep inspiration breath holding (DIBH) in comparison with free-breathing in the tattoo group. The patients were immobilised with arm supports. A total dose of 26 Gy for the breast was prescribe in 5 daily fractions and a concomitant boost in the surgical bed of 29 Gy was allowed following the center protocol. The treatment was calculated with Pinnacle® and delivered with a VERSA HD® .A daily CBCT was perform for all patients. The Longitudinal (Y), Lateral (X) and Vertical (Z) positions swift were filed in Mosaiq. If a shift more than 0,5 cm was present at treatment an online review was performed by a Radiation Oncologist. We registered the following parameters: age, stage, daily shift recorded in Mosaiq.T–student was used to compare the two modalities. A second analysis was perform differencing right and left breast considering the two different techniques available DIBH and free- breathing. Results A total of 300 fractions was done. A median age of 66 years old. 83% were stage IA and 17% stage IIA. 28 patients received concomitant boost. In the first group, a median of shift of X= 0.2 cm Y=0.16 cm Z=0. 1 cm was registered and in the second group: X= 0.3 cm Y= 0.2 cm Z= 0.3. 39 patients received right breast cancer radiotherapy, divided equally in the two groups, a median shift of SGRT group: X=0,1 cm; Y=0.1 cm; Z= 0.31 cm and X=0,1 cm; Y=0.2 cm; Z= 0.17cm in the tattoo group with no statistical difference (p= 0,65; p= 0.38; p=0.13, respectably) 24 patients undergone left breast radiotherapy, 12 patients in each group. A media shift registered in the Tattoo group: X= 0,1 cm; Y= 0.26 cm; Z= 0.31 vs X= 0,1 cm; Y= 0.3 cm; Z= 0.2cm in SGRT. Vertical movements improved in the SGRT group with a statistical difference (p=0.002). When comparing all patients a statistical difference was found in Z (p=0.006).

Conclusion

SGRT improves patient positioning accuracy compared to tattoos in left breast cancer patient treated with DIBH. In the right sided breast treatment SGRT is an available possibility for set up with no statistical difference compare to tattoos.

PD-0655 The design and construction of a simulated linac control area (SLCA) for Radiation Therapy