ESTRO 2022 - Abstract Book

S1637

Abstract book

ESTRO 2022

Conclusion After performing pitch and roll on the setup CBCT the required corrections on the verification CBCT vary widely. There is a moderate correlation between the magnitude of pitch and the longitudinal correction and a strong correlation between the magnitude of roll and the lateral correction. Very similar statistical data and correlation coefficients show that the subgroups of breast cancer patients correspond to those for the entire group and that the stability of breast cancer patients is comparable to lung cancer patients.

PO-1844 Evaluation on Bra usage for breast cancer radiotherapy: OARs sparing and acute skin reaction

S.T. Chiu 1 , S.M. Wong 1 , S.W. Kong 1 , W.Y. Lee 1 , K.F. Cheng 1 , G. Chiu 1

1 Hong Kong Sanatorium & Hospital, Department of Radiotherapy, Hong Kong, Hong Kong (SAR) China

Purpose or Objective Radiotherapy is part of the common treatment regime for Ca Breast Patient. During the radiotherapy treatment, patient is usually treated without wearing any bra or clothes. The breast tissue was treated in nature position without any immobilization device. In recent year, a commercial FDA-approved bra is available for the use in radiotherapy treatment. This study aims to evaluate the Chabner® XRT bra in the term of dosimetric effect on OARs (heart and ipsilateral lung) sparing and the seriousness of acute skin reaction. Female breast cancer patients with a self-reported breast cup size of B or above, who haven’t undergone mastectomy, were recruited prospectively for this study. With the consent of patient, two set of CT images (with and without bra) were taken for treatment planning. All borders were defined by a single oncologist. Two treatment plans (with and without bra) using 2-field tangential opposing technique were computed for dosimetric comparison. The maximum lung depth, the field length and DVH parameters, including Dmean of heart, V20, V10 and V5 of ipsilateral lung, were used for comparison. Acute Skin Reaction All breast cancer patients underwent 2-field tangential breast conformal radiotherapy from 2019-2021 at Hong Kong Sanatorium & Hospital were recruited retrospectively. Their acute radiation-induced skin reactions were compared between patients treated with bra and without bra using the acute radiation morbidity scoring criteria (Grade 0-4) suggested by RTOG, which the detail is shown as follows. 0 No change over baseline 1 Follicular, faint or dull erythema/epilation/dry desquamation/ decreased sweating Materials and Methods OARs Sparing

2 Tender or bright erythema, patchy moist desquamation/ moderate edema 3 Confluent, moist desquamation other than skin folds, pitting edema 4 Ulceration, haemorrhage, necrosis Table 1: The acute radiation morbidity scoring criteria (Grade 0-4)

Results A total of 18 treatment plans from 9 patients (6: Ca Rt Breast; 3: Ca Lt Breast) were computed and used for dosimetric comparison. For patients with bra, the inferior border shifted 1.2 cm superior and the lateral border shifted 0.8cm on average. The maximum lung depth decreased 0.3cm (2 vs 2.3cm; p=0.03). The V20, V10, V5 of ipsilateral lung has a