S267
Clinical - Breast
ESTRO 2026
Torrisi 2 , Antonella Del Vecchio 1 , Tiziana Rancati 3 , Nadia Gisella Di Muzio 2,4 , Claudio Fiorino 1 1 Medical Physics, IRCCS San Raffaele Scientific Institute, Milan, Italy. 2 Radiation Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 3 Data Science Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy. 4 Faculty of Medicine and Surgery, Vita- Salute San Raffaele University, Milan, Italy Purpose/Objective: Cardiac calcifications (CAC) are emerging as predictors of cardiac toxicity after breast cancer Radiotherapy. Main purposes of this study were: to test the association between CAC scores and specific subgroups of cardiac events in a cohort treated with moderate hypo-fractionation; to assess interplay with dosimetry/clinical predictors for different families of events. Material/Methods: Data of 1172 consecutive patients treated at our hospital with 3DCRT whole breast irradiation (40Gy/15fr) were available. Participants with pacemakers/defibrillators were excluded; 1091 patients remained . Heart was automatically segmented, and the mean heart dose (MHD) was assessed. The Agatson score (AS), the CAC_volume and the max HU value in the heart (Max_HU) were quantified using an in-house script. Other clinical parameters were available, including laterality, chemotherapy, age, smoking and respiratory toxicity occurring during the first 3 years after Radiotherapy. Cardiac events were classified into two categories: CAC_corr, the ones considered to be more directly correlated with the presence of calcifications (Coronary artery disease, Acute myocardial infarction, Congestive heart failure and heart valve disease); CAC_uncorr, the remaining ones (Conduction abnormality, Atrial premature beats, Atrial fibrillation, Pericarditis and Tachyarrhythmia). The association between variables and cardiac events subgroups was tested by logistic regression. Results: 29 patients experienced cardiac events (median follow-up:6.5y), 15 belonged to the CAC_corr group (8/15 right breast cancer); regarding CAC_uncorr, only one patient was treated for right breast cancer; then, analyses were restricted to the left breast patients (13 events out of 561 patients). For CAC_corr, AS/CAC_volume/Max_HU (considered one at a time) and Age were the main predictors (AUC=0.80/0.79, p<0.0001). Lung toxicity (occurring in 18 patients in total) did not impact the results.
estimate outcomes. Results:
Median age was 48 years (IQR 47-52). Median follow- up was 25.6 months (std 11.29; IQR 13.45-34.27). Five patients (7.1%) were T1a, 26 (37.1%) T1b, 30 (42.8%) T1c and 6 (8.5) T2. One (1.4%) was T1mi and 2 were ypT0 and ypT1a respectively. Three (4.2%) were N1a. Twenty (28.5%) were G3 and 8 (11.4%) were Triple Negative. 3 months after RT, Grade 1 fibrosis occurred in 15/70patients (21.4%), Grade 2 fibrosis occurred in only 1 patient (1.4%). At 6 months Grade 1 fibrosis occurred in 14/70 patients (20%), Grade 2 fibrosis occurred in only 2 patients (2.8%). Only one patient developed Grade 3 dermatitis at 3 months, which was resolved with topical therapy. Table shows the entire toxicities of all patients. One patient experienced a local recurrence after 12.6 months. LR at 12 and 18 months were 0% and 1.8%. MFS and OS were 100% at 24 months.
Conclusion: This phase II clinical trial demonstrates that a single- fraction stereotactic boost to the surgical cavity using GammaPod™ is safe and associated with minimal toxicity for patients with early-stage breast cancer. We will soon begin enrolling patients for a boost study following completion of the 5-fraction Fast Forward regimen. Keywords: Single-Fraction Boost, in High-Risk Breast Cancer
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Predictors of cardiotoxicities after hypo- fractionated whole breast radiotherapy: dependence on the type of cardiac event
Alfonso Belardo 1 , Andrei Fodor 2 , Marco Fois 1 , Bjorn Kerby Dimayuga 1 , Lucia Perna 1 , Laura Giannini 2 , Paola Mangili 1 , Gabriele Palazzo 1 , Marcella Pasetti 2 , Miriam
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