ESTRO 2024 - Abstract Book

S457

Clinical - Breast

ESTRO 2024

The majority of breast cancer patients (>70%) can be treated with breast conserving therapy (BCT) consisting of surgical complete removal of the tumor followed by irradiation of the breast. With increasing life expectancy, long term treatment related side effects affecting quality of life (QoL) become increasingly important. Unfortunately, breast fibrosis occurs as a late adverse event in a substantial subset of patients (10-30%) of which 2-5% is severe. Fibrosis can lead to breast retraction, breast asymmetry, pain and can be an unwanted reminder of BCT. Besides patient- and tumor related factors, both surgery and radiotherapy play a role in the risk of developing fibrosis. The STARLINGS study (ClinicalTrials.gov ID: NCT05263362) was set up to assess the role of different combinations of (oncoplastic) surgery and radiotherapy techniques, for the development of moderate to severe fibrosis and moderate to poor cosmetic outcome. In this preliminary study we assessed the relation between the presence and severity of fibrosis, cosmetic outcome and QoL. Patients treated with breast conserving surgery followed by whole breast irradiation because of pT1-3N0-2 breast cancer or ductal carcinoma in situ (DCIS) were eligible for inclusion. Patients who had breast surgery other than planned or re-irradiation both after BCT, or patients who received partial breast irradiation, were excluded. Surgery was conducted between 2016 and 2020 in four Dutch hospitals and all included patients received radiotherapy in the same institute. Included patients visited the outpatient clinic one time for research purposes, respectively two to six years after BCT. During this visit, fibrosis of the whole breast and fibrosis at ‘punctum maximum’ were assessed according to Common Toxicity Criteria Adverse Event version 5.0 (CTCAE v5.0) and photographs of the breast were taken, all by one physician. Photos were analyzed using BCCT.core software to assess cosmetic outcome. The following parameters were derived and used in the analyses: pBRA (relative Breast Retraction Assessment), pLBC (relative Lower Breast Contour) and pBOD (relative Breast Overlap Difference). Quality of life was assessed by the Breast-Q questionnaire, with a difference of ten points considered clinically relevant. Patient-, tumor- and treatment characteristics were retrospectively collected from the electronic patient records. A chi-squared test was used for the comparison of the patient and treatment characteristics between the two fibrosis groups. Fisher's exact test was used for topics with low cell values. Analysis of cosmetic outcome and QoL in relation to fibrosis was done by Mann Whitney-U test. To examine the correlation between cosmetic outcome and QoL, Spearman's rank correlation coefficient was calculated. Additionally, a multivariate linear regression will be conducted in future analysis. A total of 326 patients were included and divided into two groups based on severity of fibrosis, with 245 patients in group 1 (fibrosis grade 0-1; none-mild) and 81 patients in group 2 (fibrosis grade 2-3; moderate-severe) (Table 1). Most patients were treated with simple oncoplastic techniques (195 (79.6%) group 1 vs 63 (77.8%) group 2. Nine patients in each group were treated with reduction mammoplasty (p=0.020) and eleven patients in group 1 were treated with volume replacement techniques, vs one patient in group 2 (p=0.306). Most patients in group 2 have had a boost (p<0.001). The photographs of 321 patients were eligible for analysis and 296 questionnaires were received. Evaluation with BCCT.core showed more breast retraction and asymmetry in group 2 (Table 1). This group also reported lower scores on psychosocial and physical well-being, satisfaction with breasts, and adverse effects of radiation (Table 2). Spearman’s rank test showed significant negative associations between psychosocial well -being and pBOD, and satisfaction with breasts and pBRA, pLBC and pBOD (p<0.001). Material/Methods: Results: