S682
Clinical – Lower GI
ESTRO 2026
Keywords: Recurrence, rectal cancer, neoadjuvant therapy
Digital Poster Highlight 558 Curative chemoradiotherapy and watch-and-wait management in patients with rectal cancer treated outside a clinical trial setting Ellen Lund Schaldemose 1 , Birgitte Mayland Havelund 1 , Lars Henrik Jensen 1,2 , Mette Møller Sørensen 3,2 , Bjarke Mortensen 4 , Lars Ulrik Fokdal 1,2 1 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark. 2 Department of Regional Health Research, ospital of Southern Denmark, Odense, Denmark. 3 Department of Surgery, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark. 4 Department of Medical Physics, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark Purpose/Objective: Radical surgery, often combined with preoperative (chemo)radiotherapy (CRT), is standard care for rectal cancer. Curative CRT with watch-and-wait (WW) management represents an alternative to surgery, especially for patients wishing to avoid a stoma or surgical morbidities. CRT is often delivered in clinical trials, but some patients are ineligible due to frailty, comorbidities, or other malignancies. This study evaluates outcomes in these patients. Material/Methods: Consecutive patients with rectal cancer receiving CRT outside of clinical trials at our institution between 2015–2025 were included. Radiotherapy consisted of 50.4 Gy to the elective target with a tumor/lymph node boost to 62 Gy in 28 fractions using VMAT or IMRT technique. Capecitabine (825 mg/m ² twice daily) was prescribed to fit patients.Follow-up included a WW program with endoscopy and imaging: every 3 months in year 1, every 4 months in years 2–3, and every 6 months in years 4–5. Patient demographics, disease characteristics, and treatment outcomes were analyzed descriptively and by Kaplan-Meier estimates. Toxicity was assessed with CTCAE v3.0. Results: Of 206 rectal cancer patients treated with CRT, 50 (24.7%) were managed outside trials. Median age was 72 years (range 47–84), with half presenting moderate or severe comorbidities. Tumour stage distribution was cT1: 28%, cT2: 36%, cT3: 36%. Enlarged lymph nodes were found in 38%; and 4% had oligometastatic disease (table 1). Two patients (4%) discontinued radiotherapy early, and six (16.6%) out of 36 patients stopped capecitabine due to toxicity. The remaining 43 (86.0%) completed planned treatment.Median follow- up was 58 months (range 4–124). Five patients did not
Conclusion: Histopathological features prove to be the strongest prognostic indicators in rectal cancer, compared to clinical and treatment-related characteristics. Hence, it is the dynamic tumor response to neoadjuvant therapy that is most predictive of recurrence risk and long-term prognosis. These findings underscore the need for reliable biomarkers that can predict tumor response at baseline, thereby enabling the selection of the most optimal treatment for each individual rectal cancer patient. Although early recurrence negatively impacts OS, survival measured from the time of recurrence is similar between early and late recurring patients. References: 1. Bahadoer RR et al. Lancet Oncol 2021;22:29–42.2. Conroy T et al. Lancet Oncol 2021;22:702–15.3. Garcia- Aguilar J et al. J Clin Oncol 2022;40:2546–55.4. Fokas E et al. J Clin Oncol 2019;37:3212–22.5. Hofheinz R-D et al. Ann Oncol 2025; doi:10.1016/j.annonc.2025.05.528.6. Scott AJ et al. J Clin Oncol 2024; doi:10.1200/JCO.24.01160.
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