S725
Clinical – Lower GI
ESTRO 2026
Siemens Healthineers). All patients received three cycles of preoperative chemotherapy. Treatment response was assessed with pelvic MRI and colonoscopy. Patients with no residual tumour on imaging and endoscopy were offered active surveillance; the remaining patients underwent surgery. Pathological response was evaluated in resected specimens. Side effects were evaluated according to standard criteria. Results: A total of 43 patients were enrolled, including 24 men, with a median age of 66 years (range 37–80). Eleven patients met the criteria for active surveillance, showing no visible tumour on MRI or endoscopy. The remaining thirty-two patients underwent surgery. Pathological complete response after neoadjuvant therapy was confirmed in 8 patients, and 5 patients demonstrated near-complete response. No grade ≥ 3 gastrointestinal or urinary adverse events were observed. Conclusion: Our preliminary results suggest that dose-escalated short-course radiotherapy using SIB is feasible, well- tolerated, and shows promising results in patients with locally advanced rectal cancer. Keywords: rectal cancer, neoadjuvant treatment Tailored radiotherapy strategies for early stage rectal cancer: 10-year follow-up of a de-escalation prospective study Pasquale Trecca 1 , Michele Fiore 1 , Gabriele D'Ercole 1 , Gian Marco Petrianni 1 , Alice Tretola 1 , Damiano Caputo 2 , Roberto Coppola 2 , Edy Ippolito 1 , Sara Ramella 1 1 Radiation Oncology, Fondazione Policlinico Universitario Campus Bio-Medico di Roma, Roma, Italy. 2 Department of Surgery and Research Unit of General Surger, Fondazione Policlinico Universitario Campus Bio-Medico di Roma, Roma, Italy Purpose/Objective: To assess the long-term recurrence rates and clinical outcomes of patients with locally advanced rectal cancer treated with neoadjuvant chemoradiation in a prospective protocol with de-escalated radiation volumes by omitting elective pelvic lymph node irradiation. Material/Methods: Digital Poster Highlight 3456 This study included 52 patients with rectal T2 low- lying/T3, N0-N1 tumors without evidence of lateral lymph node involvement, as assessed by computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/CT (PET/CT). The clinical target volume included the primary tumor and
successfully completed the intended CRT regimen and subsequently underwent TME after restaging MRI, with a median interval of 11 weeks (range 7–18). The median operative time was 255 minutes (range 200– 455). Major postoperative complications (Clavien– Dindo ≥ 3) occurred in nine patients (12%). An intact mesorectum (Quirke grade 3) was achieved in 67 patients (93%), while the pathological complete response (pCR) rate was 27% (n = 20). Although the SIB-CRT group showed a longer median interval to surgery (12 vs. 10 weeks, p < 0.001), no significant differences were found between groups in operative duration, mesorectal integrity, complication rates, or pCR incidence. Conclusion: SIB-CRT did not compromise surgical outcomes compared with conventional CRT. Considering the high pCR rates in both cohorts, further prospective studies with larger sample sizes are warranted to clarify the potential therapeutic advantage of this intensified approach Keywords: SIB; Rectal Cancer; Surgical outcomes Digital Poster Highlight 3428 Short course radiotherapy with dose escalation improves tumour response Tomasz Wi ś niewski 1,2 , Karina Korzybska 2 , Manuela Las- Jankowska 3,4 , Izabela Zar ę bska 2 , Maciej Blok 2,5 , Micha ł Jankowski 3,6 , Maciej Harat 2,5 , Roman Makarewicz 1 1 Department of Oncology and Brachytherapy, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Bydgoszcz, Poland. 2 Department of Radiotherapy, Franciszek Lukaszczyk Oncology Centre, Bydgoszcz, Poland. 3 Department of Oncological Surgery, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Bydgoszcz, Poland. 4 Chemotherapy Outpatient Clinic, Franciszek Lukaszczyk Oncology Centre, Bydgoszcz, Poland. 5 Center of Medical Science, University of Science and Technology, Bydgoszcz, Poland. 6 Clinical Department of Oncological Surgery, Franciszek Lukaszczyk Oncology Centre, Bydgoszcz, Poland Purpose/Objective: To evaluate the feasibility, safety and efficacy of short- course radiotherapy with simultaneous integrated boost (SIB) combined with sequential chemotherapy as neoadjuvant treatment for patients with locally advanced rectal cancer. Material/Methods: This single-arm, single-institution phase II study included patients with locally advanced rectal cancer treated with SIB radiotherapy to a total dose of 30 Gy in 5 fractions using a tomotherapy system (Halcyon,
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