S738
Clinical – Lower GI
ESTRO 2026
Conclusion: Neoadjuvant Rectal (NAR) score, originally validated as a surrogate endpoint for overall survival, shows promise as a specific and practical predictor for the risk of early distant metastases. The NAR score could be used to precisely identify the subgroup of patients who, despite receiving intensive TNT, harbor a particularly poor prognosis due to a high risk of early systemic relapse. The conclusions are pending further validation in larger studies. References: Neoadjuvant Rectal (NAR) Score: a New Surrogate Endpoint in Rectal Cancer Clinical Trials. T.J. George Jr., C. J. Allegra, G. Yothers, Curr Colorectal Cancer Rep (2015) 11:275–280 Short-course radiotherapy followed by chemotherapy before total mesorectal excision (TME) versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO): a randomised, open- label, phase 3 trial Bahadoer, Renu RØstergaard, L. et al. The Lancet Oncology, Volume 22, Issue 1, 29 – 42Garcia-Aguilar et al.. Organ Preservation in Patients With Rectal Adenocarcinoma Treated With Total Neoadjuvant Therapy. J Clin Oncol. 2022 Aug 10;40(23):2546-2556. doi: 10.1200/JCO.22.00032. Epub 2022 Apr 28. Keywords: rectal cancer, NAR score, TNT Organ preservation in rectal cancer by " MR -guided online Adaptive dose-escalated Radiotherapy for Rectal Sparing" (MARS) . Cihan Gani 1 , Monica Lo Russo 1 , Barbara Gehler 1 , Daniel Zips 2 , Michael Bitzer 3 , Rüdiger Hoffmann 4 , Robert Bachmann 5 , Ulrike Schempf 3 , Marcel Nachbar 1 , Daniela Thorwarth 1 , Sabrina Baumeister 1 , Sarah Kübler 1 , Jessica Boldt 1 , Kristina Mac Millan 1 , Maximilian Niyazi 1 , Simon Boeke 1 1 Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 2 Radiation Oncology, Charite Hospital Tübingen, Tübingen, Germany. 3 Internal Medicine, Gastroenterelogy, University Hospital Tübingen, Tübingen, Germany. 4 Radiologie, University Hospital Tübingen, Tübingen, Germany. 5 Surgery, University Hospital Tübingen, Tübingen, Germany Poster Discussion 4412 Purpose/Objective: Rectal tumors are challenging to treat with dose- escalated radiotherapy due interfractionaltumor motion, shrinkageand the limited visibility of these tumors on cone-beam CT based linear accelerators. For thisreason,we developed a novel protocol (“MARS”) for online adaptive MR-guided dose escalation with the goal of organ preservation. Material/Methods:
Patients with non-circumferential rectal cancer seeking non-operative management were scheduled for long- course chemoradiotherapy with 50 Gyor 50.4 Gy to the primary tumor and the pelvic lymphaticswith concomitant chemotherapy with 5-FU or Capecitabine.In addition, patients received weekly adaptive boost treatmentto the primary tumor and positive lymph nodes with 3 Gy per boost fractionon a 1.5T MR-Linacto a total of 65 Gy or 65.4 Gy. Patients with a clinical complete response (cCR) or near complete response (ncCR) were offered a watch&wait approach (w&w).Herein, we report treatment compliance, early response, overall and TME-free survivalaccording to Kaplan-Meier, adverse events according to PRO-CTCAEand rectal organ function scored by the low anterior resection syndrome (LARS) score and Wexner Score for fecal incontinence. Results: A total of 34 patients with a median age of66 years were treated with the MARS protocol.Median longitudinal tumor extension was 36 mm. T-category was T2/T3/T4 in 29% / 68% / 3% of cases. Of 34 patients, 25 (74%) received all five boost fractions.In four patients, boost fractions were discontinued due to extensive tumor shrinkage,and in four patients due to adverse events. Grade 3 / 4 diarrhea during chemoradiotherapy was reported by 23% of patients. Twelve patients (35%) received consolidation chemotherapy. At restaging, 31/34 patients (91%) achieved a ncCRor cCR. Median follow- up was 20 months. Two-year overall and TME-free survival were100% and 83%.No significant differences were observed from baseline to 24-month follow-up for Wexner (2.53 vs 3.05, p = n.s.) and LARS score (16.10 vs 20.91, p = n.s.).
Made with FlippingBook - Share PDF online