ESTRO 2024 - Abstract Book

S594

Clinical - Breast

ESTRO 2024

Montagne L, Hannoun A, Hannoun-Levi JM. Second conservative treatment for second ipsilateral breast tumor event: A systematic review of the different re-irradiation techniques. Breast. 2020;49:274-280. doi:10.1016/j.breast.2020.01.003

Elfgen C, Güth U, Gruber G, et al. Breast-conserving surgery with intraoperative radiotherapy in recurrent breast cancer: the patient's perspective. Breast Cancer. 2020;27(6):1107-1113. doi:10.1007/s12282-020-01114-y

2005

Poster Discussion

Irradiation of organs at risk may have adverse effects on survival in breast cancer patients

Stefanie A. de Boer 1 , Daan S. Spoor 1 , John H. Maduro 1 , Nanna M. Sijtsema 1 , Suzanne P.M. de Vette 1 , Lisanne V. van Dijk 1 , Gert Sikkema 1 , Martijn Veening 1 , Ewoud Schuit 2 , Johannes A. Langendijk 1 , Anne P.G. Crijns 1 1 University Medical Center Groningen, Radiation Oncology, Groningen, Netherlands. 2 University Medical Center Utrecht, Utrecht University,, 2Julius Center for Health Sciences and Primary Care, Utrecht, Netherlands

Purpose/Objective:

Breast cancer (BC) survivors treated with adjuvant radiotherapy may suffer from radiation-induced complications caused by incidental dose to surrounding organs at risk (OARs). Recent studies including patients with other thoracic cancers like lung- and esophageal cancer showed that increasing heart and lung dose are associated with worse overall survival (OS). Except the heart and the lungs, another possible recently recognized OAR in thoracic cancers is the immune system. It has been hypothesized that circulating immune cells like lymphocytes in the blood can influence tumor control and are known to be radiosensitive. Therefore, the primary aim of this study was to test whether mean heart dose (MHD), mean lung dose (MLD) and effective dose to the immune cells (EDIC) affect survival in BC patients.

Material/Methods:

Data from 3,423 patients (median age 59 years) treated with RT (41.6 – 67.2 Gy) for stage I to III invasive BC between January 2005 and June 2015 were analysed. Patients were excluded if they had recurrent disease at study entry, history of other malignancies (except for non-melanoma skin cancers), received prior or partial breast RT, or bilateral BC. Multiple imputation by chained equations (10 times) was applied to deal with missing data. The EDIC was computed as equivalent uniform dose to the entire blood based on radiation doses to all blood-containing organs (according) to the model designed by Jin et al (1). Cox proportional hazard regression models were used to estimate the hazard ratios (HRs) for the association between MHD, MLD, EDIC and the outcomes BC specific survival (BCSS), overall survival (OS), local regional recurrence (LRR) and distant metastasis (DM). Since it is possible that the association is distorted by other common causes of premature death and BC recurrence we also adjusted for possible confounding factors like age in categories, smoking status, T classification, N classification, BC laterality, tumour grade, lymphovascular invasion, molecular subtype, chemotherapy, cardiovascular risk factors, previous cardiovascular disease, and radiation treatment schedule.