S21
Brachytherapy - Gastro-intestinal, paediatric brachytherapy, miscellaneous
ESTRO 2026
organ preservation in early cT2-cT3 rectal adenocarcinoma (OPERA): a phase 3, RCT. Lancet Gastroenterol Hepatol. 2023 Apr;8(4):356-367. 3. Bahadoer RR, et al. SCRT followed by chemotherapy before TME versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO): a randomised, open- label, phase 3 trial. Lancet Oncol. 2021 Jan;22(1):29- 42. Endorectal high dose rate adaptive brachytherapy boost for treatment of T2-3N0-2 low rectal cancer: probability of complete response. Sergey Nikolaevitch Novikov 1 , Tiuriaeva Elena 1 , Novikov Roman 1 , Samsonov Denis 2 , Grishko Pavel 3 , Grinkevich Marina 4 , Karachun ¹ Alexey 2 , Tkachenko Oleg 4 , Sergey Kanaev 1 1 Radiotherapy, N.N. Petrov Cancer Institute, St Petersburg, Russian Federation. 2 Rectal Surgery, N.N. Petrov Cancer Institute, St Petersburg, Russian Federation. 3 Radiology, N.N. Petrov Cancer Institute, St Petersburg, Russian Federation. 4 Endosopy, N.N. Petrov Cancer Institute, St Petersburg, Russian Federation Digital Poster 1349 Purpose/Objective: To evaluate probability of complete clinical response (cCR) to chemotherapy, external beam (EBRT) radiotherapy with endorectal high dose rate brachytherapy (ERHDRBT) boost in patients with cT2- 3N0-2 low rectal cancer. Material/Methods: Preliminary analysis was performed in 48 patients: 20- with T2N0-1, 28-T3N0-2 rectal cancer; tumour was <3cm- in 11, 3-5cm- in 27, >3cm – in 9 cases; in 28 patients tumor occupied >50% of the luminal circumference. Patients were randomized between 2 regimes of EBRT: chemoradiotherapy (23-25x2Gy+ 3CAPOX) or short coarse (5x5Gy+5CAPOX) with subsequent ERHDRBT boost on residual tumor marked on endoscopy – 3x7Gy. Results: Twelwe or more weeks after the end of radiotherapy complete clinical response (cCR) was diagnosed in 25 of 48 (52%) patients, complete pathologic response (pCR) was determined in 7 of 17 (41.2%) operated patients. In summary complete response (c С R+p С R) was reached in 32 of 48 (66.6%) cases.The types of responses according to the stage represented in the table 1; ncCR -near cCR, nonCR- non complete responseLate grade III complications were not observed, grade II – in 29% cases.Stage/responsecCR+pCRncCRnonCR с T1-2N0- 1 16/ 20, 80%2/20, 10%2/22,10% cT3N0-
The 24-36 weeks post-TNT cCR and ORR were significantly better than historical pCR (0.849[0.762,1.00]; p<0.001 and 0.876[0.794,1.00]; p<0.001, respectively). At 21 months median follow-up, there were five deaths (two disease-related), seven distant metastasis events (two after local-regrowth). 2- year local-regrowth rate, TME-free survival, DFS, and OS were estimated as 14%(95%CI:5.7%,22.9%), 72.7%(95%CI:61.3%,83.8%), 82.8%(95%CI:73.9%,92.8%) and 90%(95%CI:81.5%,99.4%), respectively, and were similar in the two arms (Figure 1).
Conclusion: Chlorophyllin significantly decreased side effects for TNT-BCT combination. Early results suggest that SCRT- based TNT combined with MR-BCT is safe, feasible and a promising approach for NOM in locally advanced rectal cancer. Keywords: Rectal Cancer, Chlorophyllin, MR- Brachytherapy References: 1. Garcia-Aguilar J, et al. Organ Preservation in Patients With Rectal Adenocarcinoma Treated With TNT. J Clin Oncol. 2022 Aug 10;40(23):2546-2556.2. Gerard JP, et al, ICONE group. Neoadjuvant CTRT with RT dose escalation with contact x-ray BCT or EBRT boost for
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