S681
Clinical – Lower GI
ESTRO 2026
Purpose/Objective: The management of locally-advanced rectal cancer has undergone a major paradigm shift in recent years with the introduction of total neoadjuvant therapy (TNT) (1- 4). However, uncertainty remains regarding the selection of the optimal TNT regimen for each individual patient (5-6). This study aimed to evalute recurrence patterns in rectal cancer to improve patient risk stratification and guide neoadjuvant treatment decision-making. Material/Methods: A prospectively collected cohort of 850 rectal cancer patients treated with neoadjuvant radio- and/or chemotherapy between 1997 and 2023 was analysed. Survival outcomes were assessed using Kaplan–Meier analysis and predictors of recurrence were evaluated with Cox proportional hazards models. Median follow- up was 12 years. Results: At 5-years, overall survival (OS) and disease-free survival (DFS) were 86.8% and 75.5%, respectively. Recurrence occurred in 167 (19.6%) patients, including 31 (3.6%) with a locoregional recurrence (LRR), 158 (18.6%) with distant metastases (DM) and 22 (2.6%) patients experiencing both LRR and DM. Recurrence- free survival (RFS) was 76.9% (95% CI: 74.1%-79.9%) at 5 years, DM-free survival (DMFS) was 77.8% (95% CI: 75.0%-80.7%) and LRR-free survival (LRFS) was 85.1% (95% CI: 82.7%-87.7%). Independent predictors of DM included lymphovascular invasion (LVI) (p<0.001), perineural invasion (PNI) (p=0.004), positive circumferential resection margin (CRM) (p=0.046) and higher lymph node ratio (LN-ratio) (p<0.001). Predictors of LRR were larger tumor diameter (p=0.025) and higher LN-ratio (p=0.047). No clinical or treatment-related factors were significantly associated with recurrence on multivariable analysis. Early recurrence was associated with higher ypN-stage, LVI, larger tumor diameter, number of examined lymph nodes and LN-ratio. Patients with an early recurrence had a worse OS than late recurring patients, while post-recurrence survival (PRS) did not differ significantly between both groups. Longitudinal analysis demonstrated a shift in rectal cancer management over the years, with neoadjuvant radiotherapy being reserved for more advanced and more distally located tumors.
Conclusion: CT-guided online ART is clinically feasible, efficient, and safe for short-course neoadjuvant radiotherapy of LACC. Daily adaptation effectively restored target coverage and reduced bowel exposure despite substantial interfractional motion. This first prospective study supports CT-linac–based ART as a practical and precise approach for integrating adaptive radiotherapy into multimodal immunochemoradiotherapy regimens for colon cancer. References: 1. Benson, A.B., et al., Colon Cancer, Version 2.2021, , 2021. 19(3): p. 329-359.2. Xia, F., et al., . J Clin Oncol, 2024. 42(28): p. 3308-3318.3. Lin, Z.Y., et al., . Ann Oncol, 2024. 35(10): p. 882-891.4. Zhang, H., et al., . BMJ Open, 2024. 14(2): p. e079442.5. Zhang, Z.T., et al., . EClinicalMedicine, 2024. 76: p. 102836.6. Chiang, C.H., T.Y. Chao, and M.Y. Huang,, 2023. 26(5): p. 487. Keywords: ART, Colon cancer, Clinical innovation Real-world evidence on long-term recurrence patterns and predictors in rectal cancer after neoadjuvant therapy Pieter Maerten 1 , Gilles Defraene 1 , Evelien Dierick 1 , Cédric Schraepen 2 , Lynn Debrun 2 , Gabriele Bislenghi 2 , André D'Hoore 2 , Freddy Penninckx 2 , Gert De Hertogh 3 , Xavier Sagaert 3 , Raphaëla Dresen 4 , Gertjan Rasschaert 5 , Sabine Tejpar 5 , Philippe Leclercq 5 , Filip Van Herpe 5 , Jeroen Dekervel 5 , Eric Van Cutsem 5 , Albert Wolthuis 2 , Karin Haustermans 1 1 Department of Radiation-Oncology, University Hospitals Leuven, Leuven, Belgium. 2 Department of Abdominal surgery, University Hospitals Leuven, Leuven, Belgium. 3 Department of Pathology, University Hospitals Leuven, Leuven, Belgium. 4 Department of Radiology, University Hospitals Leuven, Leuven, Belgium. 5 Department of Digestive Oncology, University Hospitals Leuven, Leuven, Belgium Poster Discussion 506
Made with FlippingBook - Share PDF online