S724
Clinical – Lower GI
ESTRO 2026
Digital Poster 3378 Preoperative Chemoradiation with Simultaneous- Integrated Boost: Implications for Surgical Management of Locally Advanced Rectal Cancer Mauro Loi 1 , Marianna Valzano 1 , Michele Aquilano 1 , Federico Passagnoli 2 , Francesco Coratti 2 , Pierluigi Bonomo 1 , Alessandra Galardi 1 , Laura Fortuna 2 , Daniela Greto 1 , Gabriele Simontacchi 1 , Isacco Desideri 1 , Icro Meattini 1 , Giulio Francolini 1 , Andrea Rampini 1 , Beatrice Bettazzi 1 , Matteo Mariotti 1 , Giulio Frosini 1 , Marco Banini 1 , Margherita Zani 3 , Silvia Calusi 3 , Chiara Arilli 3 , Marta Casati 3 , Giulia Cesari 1 , Fabio Cianchi 2 , Lorenzo Livi 1 1 Radiation Oncology- Careggi Hospital, University of Florence, Florence, Italy. 2 Surgical Oncology, University of Florence, Florence, Italy. 3 Medical Physics-Careggi Hospital, University of Florence, Florence, Italy Purpose/Objective: For patients with locally advanced rectal cancer (LARC), escalation of preoperative chemoradiation (CRT) with radiation boost (>50 Gy) has been proposed to enhance tumor response. Concerns have been raised regarding potential adverse effects on subsequent surgical management due to radiation-induced fibrosis, particularly with hypofractionated simultaneous-integrated boost (SIB) technique. This study aimed to compare surgical outcomes between SIB-CRT and conventional CRT in patients with LARC. Material/Methods: Clinical records of a consecutive cohort of LARC patients who underwent total mesorectal excision (TME) by the same surgical team following CRT between 2019 and 2024 were retrospectively reviewed. All patients received conventionally fractionated VMAT pelvic irradiation in 25 fractions, delivering 50 Gy (2 Gy/fraction) to the mesorectum and 45 Gy (1.8 Gy/fraction) to the elective nodal regions, concurrently with capecitabine and daily CBCT guidance; a SIB-CRT protocol delivered a total dose of 53 Gy (2.12 Gy/fraction) to the the primary tumor and pathologic lymph nodes. Demographic, clinical, pathological, and treatment-related parameters were analyzed. Results: Seventy-four patients (median age 69 years; range 37– 83) were included, of whom 25% (n = 19) with prior abdominal surgery. On baseline MRI, T4 and/or N2 stage, mesorectal fascia (MRF) involvement, and extramural venous invasion (EMVI) were observed in 15(20%), 39(52%), 22(30%), and 14(19%) patients, respectively, with no significant differences between the conventional CRT (n = 52, 70%) and SIB-CRT(n = 22, 30%) cohorts. Grade 3 acute toxicities occurred in five patients (6%), including diarrhea (n = 3), obstructive dysuria (n = 1), and anemia (n = 1). All patients
margins from the gross tumor volume with adjacent mesorectum, is not routinely adapted according to patient positioning. This study aims to evaluate mesorectal lymph node (LN) displacement between two treatment positions to avoid insufficient coverage of potentially involved LNs during target volume delineation. Material/Methods: A total of 24 patients with rectal cancer and involved mesorectal LNs were included in the study. Patients were simulated using a belly board in prone position and with a full bladder in supine position. The most superior macroscopic mesorectal LN, located above the bottom of S3 vertebra, was identified on computed tomography images. The distance from the inferior border of the delineated LN to inferior border of S3 vertebra was measured in both positions for each patient. Wilcoxon signed-rank test was used for statistical analysis. Results: The mean distance (± standard deviation) in supine and prone positions was 8.99 mm (± 1.53) and 12.79 mm (± 2.82), respectively (Table 1). The difference between the measurements in supine and prone positions was statistically significant (p < 0.0001). Lymph nodes in prone position were located more superiorly compared to those in supine position (Table 2).
Conclusion: This study revealed that patient positioning has a significant effect on mesorectal lymph node displacement. Special attention is required to include the involved LNs located superior to the tumor when determining the cranial border of the mesorectal target volume. An additional cranial margin may be considered when planning treatment in the prone position. Keywords: rectum cancer, mesorectal lymph nodes, positioning
Made with FlippingBook - Share PDF online