S710
Clinical – Lower GI
ESTRO 2026
1 Department of Radiation Oncology, GenesisCare Talavera de la Reina, Talavera de la Reina, Spain. 2 Gastrointestinal Tumor Group of the Spanish Society of Radiation Oncology (SEOR-GI), Spanish Society of Radiation Oncology (SEOR), Madrid, Spain. 3 Department of Radiation Oncology, Hospital Universitario Ramón y Cajal, Madrid, Spain. 4 Department of Radiation Oncology, GenesisCare Talavera de la Reina, Madrid, Spain. 5 Department of Radiation Oncology, GenesisCare Madrid, Hospital Universitario La Milagrosa, Madrid, Spain. 6 Department of Radiation Oncology, GenesisCare Madrid, Hospital Universitario San Francisco de Asís, Madrid, Spain. 7 Department of Radiation Oncology, Hospital Universitario de Gran Canaria Doctor Negrín, Las Palmas de Gran Canaria, Spain. 8 Department of Radiation Oncology, Hospital Carlos Haya, Málaga, Spain. 9 Department of Radiation Oncology, Institution of Ruber International Hospital, Madrid, Spain. 10 Department of Radiation Oncology, Hospital Rey Juan Carlos, Móstoles, Spain. 11 Department of Radiation Oncology, Hospital Universitario de Fuenlabrada, Madrid, Spain. 12 Department of Radiation Oncology, Hospital Universitario de Ciudad Real, Ciudad Real, Spain. 13 Department of Radiation Oncology, Hospital General Universitario de Toledo, Toledo, Spain. 14 Department of Radiation Oncology, Hospital Regional Universitario de Málaga, Málaga, Spain. 15 Department of Radiation Oncology, Complejo Asistencial Universitario de Salamanca, Salamanca, Spain. 16 Department of Radiation Oncology, Hospital Clínic Barcelona, Barcelona, Spain. 17 Department of Radiation Oncology, Hospital Universitario Gregorio Marañon, Madrid, Spain. 18 Department of Radiation Oncology, Hospital Universitario Lozano Blesa, Zaragoza, Spain. 19 Department of Radiation Oncology,
therapy (TNT) regimens, treatment selection between long-course chemoradiotherapy (CRT) and short- course radiotherapy (SCRT), inclusion of lateral pelvic nodes, use of boost, and implementation of watch- and-wait (W&W) protocols. Results: Fifty-six valid responses were received, representing most Spanish autonomous communities. TNT was implemented in all institutions; CRT followed by consolidation chemotherapy was the predominant regimen (67.9%), while induction chemotherapy prior to CRT and SCRT with consolidation were used in 51.8% and 44.6% of centres, respectively. CRT was preferred for cT3b–T4b tumours, threatened circumferential resection margin (CRM), or positive extramural venous invasion (EMVI), as well as when organ preservation was intended. Conversely, SCRT was mainly chosen for low-risk or elderly patients, or when early systemic intensification was prioritised. Lateral pelvic nodes were routinely included in 71.4% of target volumes, and 39.3% of centres reported applying an escalated boost in selected cases, most frequently as a simultaneous integrated boost (SIB, 70.4%). CRT dose was 45–50.4 Gy in 25–28 fractions, with a subset (30.4%) escalating to 52–54 Gy at the tumour or suspicious nodes. For SCRT, more than 80% did not include an additional boost. Eighty-two percent of departments reported established watch-and-wait (W&W) protocols, primarily for low-lying tumours (76.8%) or patients declining surgery (75.0%). Complete clinical response was commonly defined by negative MRI findings (92.6%), absence of endoscopic lesion (90.7%), and normal digital rectal examination (63.0%). In 75.9% of centres, the final decision was reached within multidisciplinary tumour boards, reflecting a mature implementation of organ- preserving strategies nationwide. Technologically, 98.2% of centres had image-guided radiotherapy/cone-beam computed tomography (IGRT/CBCT) and 96.4% used volumetric modulated arc therapy (VMAT) as standard, while resonance–guided linear accelerator (MR-LINAC), tomotherapy, and robotic systems remained limited but increasingly available in tertiary institutions.
Hospital Universitario Marqués de Valdecilla, Santander, Spain. 20 Department of Radiation
Oncology, Hospital Universitario Virgen del Rocío, Sevilla, Spain. 21 Department of Radiation Oncology, GenesisCare Córdoba, Córdoba, Spain. 22 Department of Radiation Oncology, Hospital MD Anderson Madrid - Hospiten, Madrid, Spain Purpose/Objective: To evaluate real-world adoption of total neoadjuvant therapy (TNT) and organ-preserving strategies among Spanish Radiation Oncology departments, following the incorporation of TNT as standard care for locally advanced rectal cancer (LARC). Material/Methods: Between May and July 2025, data were collected and analysed descriptively from an anonymous national online survey distributed to 130 radiation oncologists belonging to the Gastrointestinal Tumour Group of the Spanish Society of Radiation Oncology (SEOR-GI). The 30-item questionnaire evaluated total neoadjuvant
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