ESTRO 2025 - Abstract Book

S458

Clinical - Breast

ESTRO 2025

819

Digital Poster Lymphedema and upper arm mobility associated with breast cancer radiotherapy Tamara Jarm 1 , Nikola Besic 2,1 , Romi Cencelj Arnez 2,1 , Jasna But Hadzic 3,1 , Ivica Ratosa 3,1 1 Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia. 2 Division of Surgery, Institute of Oncology Ljubljana, Ljubljana, Slovenia. 3 Division of Radiotherapy, Institute of Oncology Ljubljana, Ljubljana, Slovenia Purpose/Objective: Breast cancer-related lymphedema (BCRL), discomfort, and shoulder mobility problems have the potential to significantly affect quality of life. Their occurrence depends on surgery and radiation therapy extent. We seek to determine if the radiation dose to healthy organs—specifically the axillary-lateral thoracic vessel juncture (ALTJ) (1), shoulder joint, irradiated lymph node regions (lymph node levels I-II versus I-IV), radiation technique (3DCRT versus IMRT/VMAT), and fractionation schedule—correlates with the specified side effects. Material/Methods: In this study, we included 306 patients with early breast cancer treated with surgery and postoperative radiation therapy. We used clinical data from the prospective database of the Early Individualized Integrated Rehabilitation Program OREH (2). Physiotherapists measured shoulder joint mobility and circumferences 15 cm above and below the olecranon prior to surgery/at baseline, 6 and 12 months after treatment to detect lymphedema, which was defined as a 2 cm discrepancy in forearm and upper arm circumference. Delineations of the ALTJ, humeral head, and humeral head PRV with a 1 cm safety margin, were performed retrospectively. Treatment planning parameters for all treatment plans were subsequently obtained. Pearson's chi-square test and multivariate analysis were used to examine categorical variables' associations. Significant differences were identified with p-value ≤0.05 (two-tailed test). Non-parametric Kruskal-Wallis was used to compare means. Results: Lymphedema and restricted upper arm mobility were observed in 123 (40.2%) and 106 (34.6%) patients, respectively, 12 months post-diagnosis. Mean radiation dose received by ALTJ (p=0.007), dose received by 98% of the ALTJ volume (p=0.0034), body mass index (p=0.046), and lymph node axillary dissection (p=0.038) were confirmed by multivariate analysis as being related with lymphedema 12 months after diagnosis. Multivariate analysis confirmed a statistically significant association between the humeral head Dmean and pain 12 months after diagnosis (p=0.036), and the association between the humeral head PRV Dmean and limited mobility 12 months after diagnosis (p=0.033). The irradiated lymph node regions, radiation technique, and fractionation schedule were not correlated with lymphedema or restricted upper arm movement. Conclusion: The irradiation of the ALTJ region correlates with the development of BCRL, while irradiation of the humeral head and PRV humeral head is linked to pain and restricted mobility of the shoulder following breast cancer treatment. More research is needed toward identifying dose to organs at risk that will be considered when planning future radiation therapy. References: 1. Gross JP, Lynch CM, Flores AM, et al. Determining the Organ at Risk for Lymphedema After Regional Nodal Irradiation in Breast Cancer. Int J Radiat Oncol Biol Phys. 2019 Nov 1;105(3):649-658. doi: 10.1016/j.ijrobp.2019.06.2509. 2. Cencelj Arnez R, Besic N, Mavric Z, et al. Evaluation of an Early Individualized Integrated Rehabilitation Program versus Standard Rehabilitation Program for Smoking Cessation in 115 Smokers Among 467 Female Breast Cancer Patients 2019-2021 in Slovenia. Med Sci Monit. 2023 Dec 2;29:e942272. doi: 10.12659/MSM.942272. Keywords: Breast cancer, radiotherapy, lymphedema