ESTRO 2025 - Abstract Book

S423

Clinical - Breast

ESTRO 2025

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Digital Poster Preliminary results of the meta-analysis of breast cancer locoregional irradiation with simultaneous versus sequential boost (BLISS) Vrushab Rao 1 , Bhooshan Zade 1 , Soumya Singh 1 , Niraj Dhawale 1 , Mansi Munshi Girme 1 , Neeraj Dhingra 1 , Shweta Mutha 1 , Sanjay Deshmukh 2 1 Department of CyberKnife Radiosurgery and Radiation Oncology, Ruby Hall Clinic, Pune, India. 2 Department of Surgical Oncology, Ruby Hall Clinic, Pune, India Purpose/Objective: The standard of treatment for early-stage breast cancer is adjuvant radiation after breast-conserving therapy (BCT), with the goal of enhancing long-term outcomes and minimising local recurrence. As an alternative to the traditional sequential boost (SEB) technique, simultaneous integrated boost (SIB) during whole breast radiation (WBRT) has gained acceptance in recent years. The BLISS meta-analysis was conducted to assess the toxicity profiles of the two boost techniques. Material/Methods: A systematic search of PubMed, Embase, Google Scholar and Cochrane Central was done for studies on WBRT with SIB or SEB. Published research from 2010 to 2024 comparing the two boost delivery modalities in terms of acute and late skin toxicity, breast induration and fibrosis, breast oedema, arm pain, or arm swelling were eligible. Data was extracted from the studies. The risk ratios (RR) were calculated and forest plots were constructed. Results: The meta-analysis included 8 randomised trials. No statistically significant difference was found between the SIB and SEB arms in terms of acute skin toxicity (RR, 0.88; Confidence Interval (CI), 0.72-1.07; P=0.21), late skin toxicity (RR, 0.93; CI, 0.66-1.03; P=0.65), breast pain (RR, 0.95; CI, 0.81-1.11; P=0.49), breast induration and fibrosis (RR, 0.94; CI, 0.76-1.15; P=0.55), and arm lymphedema (RR, 0.88; CI, 0.66-1.19; P=0.41). Though a statistically significant difference was found in breast edema rates (RR, 0.67; CI, 0.45-0.99; P=0.04), with the incidence being higher in the SEB arm, a significant heterogeneity was detected (0.03), suggesting inconsistent effects in magnitude and/or direction. The I 2 value indicates that 68% of the variability among studies arises from heterogeneity rather than random chance. The difference in breast edema rates were also proved to be statistically insignificant. Conclusion: The preliminary results of the BLISS meta-analysis shows that whole breast radiotherapy with simultaneous integrated boost to the tumour bed is non-inferior in terms of acute and late toxicities when compared with sequential boost to the tumour bed.

Keywords: Breast cancer radiotherapy, boost, meta-analysis

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Digital Poster MRI Radiomic Analysis of Radiation-Induced Morphea of the Breast: A Proof-of-Concept Study Alexander Michael Stessin 1 , Jieying Wu 1 , Joseph Baer 2 , Samuel Ryu 1 , Prateek Prasanna 2 1 Radiation Oncology, Stony Brook University Medical Center, Stony Brook, USA. 2 Department of Biomedical Informatics, Stony Brook University Medical Center, Stony Brook, USA

Purpose/Objective: Radiation-induced morphea (RIM) is a very rare but devastating side effect of breast radiation therapy,