ESTRO 2023 - Abstract Book

S997

Digital Posters

ESTRO 2023

In addition to the spontaneous, abdominal and thoracic DIBH maneuvers found in the literature, a combination of abdominal and thoracic DIBH were included in this study. Breath hold in a comfortable exhale was included as a proxy for free breathing. A 3D T1-weighted DIXON-VIBE MR-sequence was used to image the research participants performing the five different breath hold maneuvers (Siemens Aera, 1,5 T). The scan time was 17-19 s, depending on the field of view (FoV). The whole breast, heart and ipsilateral lung were delineated according to national guidelines (SWEBCG). The MRI data was segmented in bulk densities for CT-number assignments and treatment planning was performed using the 3DCRT technique (Eclipse, Varian Medical Systems). Results The mean absorbed dose to the heart and ipsilateral lung were evaluated for the five different breath hold maneuvers (Figure 1). The trend of the result for the volume of the lung receiving 40% of the prescribed dose (40,05 Gy) was similar to the result for the mean absorbed dose to the lung (not shown).

Conclusion In this small-scale pilot study for left-sided breast tangential 3DCRT, all the investigated DIBH maneuvers were found to be beneficial regarding the mean absorbed dose to the heart. Even though the result for all DIBH maneuvers were well below the restriction criteria for the lung, DIBH was not always optimal regarding mean absorbed dose and the volume receiving 40% of the prescribed dose for the lung. Further investigation will include axillary, fossa supraclavicular and internal mammary lymph nodes in the CTV and the data will be evaluated for a more extensive cohort of research participants. VMAT planning will be included as well.

References:

1. Korreman et al. Rad Onc 2005 2. Zhao et al. Rad Onc 2018 3. Oechsner et al. Rad Onc 2019 4. Latty et al. J Med Radiat Sci 2015

PO-1245 Breast cancer radiotherapy's impact on shoulder morbidity: Towards the consideration of a new OAR?

Z. Naimi 1 , M. El Bessi 1 , M. Bohli 1 , R. Ben Amor 1 , A. Hamdoun 1 , R. Haddad 1 , L. Kochbati 1

1 Abderrahmen Mami Hospital, Radiation Oncology Department, Ariana, Tunisia

Purpose or Objective The aim of this study was to assess shoulder’s exposure in hypofractionated 3D conformal breast cancer radiotherapy with regional lymph nodes irradiation (RNI), and to analyse the correlation between dosimetric parameters and late patient reported outcomes involving shoulder/arm morbidity. Materials and Methods A total of 276 breast cancer patients treated with regional lymph nodes radiotherapy between 2018 and 2020, were included in this study. All patients underwent 3D conformal hypofractionated radiotherapy with a prescription dose of 40.05 Gy delivered in 15 daily fractions +/- an additional boost of 13.35 Gy. For each patient, the shoulder was contoured including all bone structures (humeral head, acromion, coracoid process and scapula), muscles and soft tissues in the shoulder region, extending 2cm caudally to the inferior slice of the supraclavicular CTV. Dose volume histograms were analysed and the following dosimetric parameters to the shoulder were calculated: V5Gy, V10Gy, V30Gy, Dmean, Dmax. Late shoulder morbidity (> 6 months) was assessed using the quick disabilities of the arm, shoulder, and hand (q-DASH) questionnaire. Statistical associations between the q-DASH scores and dosimetric parameters to the shoulder were analysed. Results The mean Dmean/Dmax to the shoulder was 8.82 Gy/21.69 Gy. The mean V5 Gy, V10 Gy, and V30 Gy were respectively 639 cc, 521 cc and 408 cc. Chest wall radiotherapy yielded higher doses to the shoulder when compared to radiotherapy to the remaining breast (p<0.01). Shoulder exposure was substantially higher when berg levels 1 and 2 were irradiated. After a