ESTRO 2025 - Abstract Book

S1242

Clinical – Lower GI

ESTRO 2025

Material/Methods: It was a retrospective review of a prospectively maintained database from AMCGH in Bangladesh where we identified 268 patients from January 2019 to June 2021 who full-filled the following criteria: cT3 or cT4a, clinically node positive, with or without involved mesorectal fascia, aged 18-70yrs, ECOG performance status 0-1. All patients had received neo-adjuvant CCRT through 3DCRT technique, 45Gy/25# followed by 5.4Gy/3# with concurrent capecitabine 825mg/m2 followed by 4 to 5 cycles chemo (XELOX). Surgery – Total Mesorectal Excision (TME) was done 6 to 8 weeks after completing chemotherapy. Our primary endpoints were locoregional failure rate, pathological complete response (PCR) after surgery and factors behind not achieving PCR. Secondary endpoints were PCR after CCRT, locoregional recurrence free survival, disease free survival, acute and delayed radiation related toxicities (documented according to CTCAE-Common Terminology Criteria for Adverse Events: version 5.0) Results: Total 268 patients were eligible who meets the inclusion criteria. At three years median follow up, Locoregional failure rate was 25% (67/268) and PCR (no residual disease after surgery) was found in 28% (75/268) of patients. Factors that hinder PCR were: advanced T stage, mucinous histopathology, high grade, stable MSI; clinically positive nodes, delay in starting treatment, any gap during treatment. Conclusion: At the end of study, we come to this point that improving PCR should be our primary concern as we found PCR after CCRT and surgery are important demarcations for achieving long term better outcome. For this we have to educate our people for early screening, diagnosis and treatment. References: Amariyil, A., Pathy, S., Sharma, A., Kumar, S., Pramanik, R., Bhoriwal, S. and Pandey, R.M., 2024. Randomized Controlled Trial of Neoadjuvant Short-Course Radiotherapy Followed by Consolidation Chemotherapy Versus Long-Course Chemoradiotherapy in Locally Advanced Rectal Cancer: Comparison of Overall Response Rates. Journal of Gastrointestinal Cancer , 55 (1), pp.373-382. Turri, G., Ostuzzi, G., Vita, G., Barresi, V., Scarpa, A., Milella, M., Mazzarotto, R., Ruzzenente, A., Barbui, C. and Pedrazzani, C., 2024. Treatment of locally advanced rectal cancer in the era of total neoadjuvant therapy: a systematic review and network meta-analysis. JAMA Network Open , 7 (6), pp.e2414702-e2414702. Keywords: Rectal cancer, Pathological complete response Digital Poster short-course strategy for rectal cancer: for whom and why? a real-world exploratory analysis Marianna Alessandra Gerardi 1 , Luca Bergamaschi 1 , Valentina Stellari 1,2 , Maria Giulia Vincini 1 , Mattia Zaffaroni 1 , Vincenzo Bagnardi 3 , Samuele Frassoni 3 , Cristiana Fodor 1 , Maria Giulia Zampino 4 , Davide Ciardiello 4 , Simona Borin 5 , Uberto Fumagalli Romario 5 , Annamaria Ferrari 1 , Maria Cristina Leonardi 1 , Barbara Alicja Jereczek-Fossa 1,2 1 Division of Radiation Oncology, European Institute of Oncology IRCCS, Milan, Italy. 2 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy. 3 Department of Statistics and Quantitative Methods, University of Milan-Bicocca, Milan, Italy. 4 Division of Gastrointestinal Medical Oncology and Neuroendocrine Tumors, European Institute of Oncology IRCCS, Milan, Italy. 5 Digestive Surgery, European Institute of Oncology IRCCS, Milan, Italy Purpose/Objective: Short-course radiotherapy (SCRT) is an effective strategy for locally advanced rectal cancers (LARCs) in a neoadjuvant setting: it means only one-week RT, with a low impact on patients (pts)’ routine, and a benefit in terms of healthcare costs and waiting list, comparing to long-course RT. Its use also finds a clinical rationale in metastatic pts, to achieve local disease control. Moreover, the choice of scheduling immediate or deferred surgery after SCRT 3476