S9
Track-Topic
ESTRO 2026
1 Radiation Oncology, Fundación IMOR-Atrys Health, Barcelona, Spain. 2 Breast Surgery, Unidad de Senologia Avanzada, Barcelona, Spain. 3 Physics and Radiation Protection, Fundación IMOR-Atrys Health, Barcelona, Spain. 4 Clinical Dosimetry, Fundación IMOR-Atrys Health, Barcelona, Spain. 5 Radiation Oncology, Instituto de Oncologia Avanzada-Atrys Health, Barcelona, Spain. 6 Nuclear Medicine, Hospital Universitario Sagrado Corazón, Barcelona, Spain. 7 Radiation Oncology, Hospital del Mar, Barcelona, Spain Purpose/Objective: The aim of this abstract is to compare the irradiated boost volumes with EBRT-VMAT boost and Targeted Intraoperative Radiotherapy (TARGIT) boost with the hypothesis that boosting with intraoperative radiotherapy immediately after lumpectomy reduces the irradiated breast volume. Material/Methods:
of 0.9 cm. Most tumors were IDC (63.6%) and ER- positive (93.8%). Median follow-up was 6.4 years (IQR: 5.0, 8.0). Most patients initiated endocrine therapy (78.0% of eligible). The estimated 5-year cumulative incidence of IQTR was 4.1% (90% CI 2.8-5.8%) (Figure), with a 5-year IQTR-free survival of 93.1%. Whether PB- IORT was delivered pre- or post-pathology [3.6% (90% CI, 2.0-6.0%) vs. 6.2% (90% CI, 2.5-12.9%), Gray’s p=0.65], the 5-year cumulative incidences of IQTR were comparable. Loco-regional and distant recurrence rates were 1.2% (90% CI, .5-2.5%) and 0.6% (90% CI, .2- 1.8%), respectively. Five-year overall survival was 97.2%; only 3 of 19 deaths were attributable to breast cancer. Toxicities were infrequent: 239 (67%) participants experienced any AE, but only 12 (3%) experienced grade 3 or 4 AEs. Most patients (91%) had good/excellent cosmesis at 2 years.
A comparative cohort trial was conducted tocomparethe boost volumes with EBRT
and intraoperativeradiotherapy. The study includes 85 patients non-suitable for APBI based on ASTRO and ESTRO criteria who underwent intraoperative radiotherapy as a boost prior to whole breast irradiation between 2014 and 2023.EBRT Boost Volume Definition: V95%: rim of tissue localized 15mm around the tumor edge plus a margin of 5mm that receives the 95% of prescribed dose (V95%) To create this volumen we include the GTV( lumpectomy cavity, clips and distortion zone) an expansion of 15mm minus the minimum reported free resection margin were added to create the CTV. The PTV is the CTV+5mm margin. An structure that encompasses the isodose of 95% was created V95%.(Figure 1).IORT Boost Volume Definition:V10mm: Rim of 1cm around the applicator, encompassing the area that receives the biological effective.To calculated the V10mm, the total volume including the applicator volume plus 10 mm marginwas obtained, then the applicator volume was subtracted from the total volume to obtain the irradiatedboost IORT volume V10mm (Figure 2).Descriptive statistical analysis was performed for both continuous and categorical variables.Normality of the continuous variables V95% and V10mm was assessed using the Kolmogorov-Smirnov test.Relationship between both variables was analyzed using Spearman and Kendall correlation coefficients.Comparison of medians was performed using the Wilcoxon signed-rank test for related samples. Results: VariableMeanMedianMinimunMaximumStandart DeviationV95%EBRT159,8cc149,8cc50,80cc324,70cc69, 97V10mm IORT 71,45cc
Conclusion: PB-IORT demonstrated durable local control, few high- grade toxicities, and excellent cosmesis. The 5-year IQTR estimate (4.1%) lies within the TARGIT-A trial’s reported confidence interval (3.3%; 95% CI, 2.1-5.1%), suggesting similar clinical outcomes while offering technical advantages of image guidance and optimized HDR dosimetry. The observed toxicity compares favorably to APBI trials. These long-term results support PB-IORT as an effective and safe approach for single-fraction radiation therapy after BCS in appropriately selected patients. Keywords: IORT, HDR brachytherapy, breast cancer
Digital Poster 1945
Comparative analysis of Radiotherapy boost volumes: Intraoperative vs External Beam Radiotherapy IVAN GARCIA ZAMORA 1 , Miguel Prats de Puig 2 , Benjamin Guix 1 , Maria Ulla Miravet 2 , Jesus Enrique Mar Silva 2 , Jose Ignacio Tello Luque 3 , David Gutierrez Roca 4 , Marco Panichi 5 , Miguel Alonso Becerra 5 , Alessio Rocchi 1 , Antonio Muñoz Garcia 6 , Manel Algara Lopez 7
Made with FlippingBook - Share PDF online