ESTRO 2023 - Abstract Book

S357

Sunday 14 May 2023

ESTRO 2023

Results Figure 1 and 2 show six interpretable factors for EORTC (529 patients) and five for CTCAE (1182 patients), respectively. Factors related to the different organs at risk are seen for both data sets. More specifically, organ-related factors for urinary (frequency, incontinence and cystitis), gastro-intestinal (diarrhea, abdominal cramps and flatulence) and vaginal (bleeding, soreness and stenosis) morbidity are identified. Furthermore, in both CTCAE and EORTC data, a factor corresponding to general symptoms is present with high loadings for fatigue, pain, insomnia, neuropathy, shortness of breath and hot flashes. Despite the fact that similar symptoms reported in the EORTC and CTCAE are defined in different ways, our results of the two factor analyses show similarity between the assessment methods in terms of main factors identified both for organs at risk and general symptoms.

Conclusion This analysis on the EORTC and CTCAE data identified syndromes which are associated with general and organ-related symptoms. Symptoms originating from a given organ often occur together, and the factor of general symptoms is consistent too. Indeed, the loadings of this factor on insomnia, fatigue and hot flashes are high in both EORTC and CTCAE, pointing to a strong influence of these symptoms in the “general symptoms” syndrome. Factor analysis is beneficial for identifying syndromes as the longitudinal correlation between symptoms is accounted for by the latent variables. Previous analyses have shown large impact of pain, fatigue, insomnia and neuropathy on QoL. This analysis shows that these symptoms have a tendency to occur together and points towards a multifactorial nature of these symptoms. OC-0453 Dosimetry Predictors of Acute Skin Reactions after Whole Breast Radiotherapy A. Cicchetti 1,2 , P. Mangili 3 , A. Fodor 4 , M. Mori 3 , A. Chiara 4 , C. Deantoni 4 , M. Pasetti 4 , G. Palazzo 4 , M.G. Ubeira Gabellini 3 , T. Rancati 2 , A. Del Vecchio 3 , N.G. Di Muzio 4,4 , C. Fiorino 3 1 San Raffaele Scientific Institute, Medical Physics, Milano, Italy; 2 Fondazione IRCCS Istituto Nazionale dei Tumori di Milano, Prostate Cancer Program, Milan, Italy; 3 San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 4 San Raffaele Scientific Institute, Radiotherapy, Milan, Italy Purpose or Objective Skin alterations and dermatitis events are usually mild and resolved after the end of breast RT. Still, for some patients experiencing moderate toxicity, the effects can be prolonged and lead to chronic symptomatology. Here, we proposed an NTCP model predicting skin toxicity using dosimetric parameters from the breast dermis to identify possible RT constraints and radiobiological assumptions on such structure. Materials and Methods The skin structure was defined as the 5 mm inner isotropic expansion from the outer CT body contour. It was retrospectively segmented on a large cohort of early-stage breast cancer patients treated between 2009 and 2017 in a single institution. Patients were treated with tangential field RT, delivering 40 Gy in 15 fractions to the whole breast without bolus application or dose boost. We preliminarily investigated the impact of changes in the dose calculation algorithms with time. Automatic delineation of the structures and DVH extractions were accomplished by scripting using the MIM_assistant software.