ESTRO 2023 - Abstract Book

S703

Monday 15 May 2023

ESTRO 2023

Conclusion High 6 month cRR were seen in both arms. sd-IMRT had more RT interruptions and chemotherapy modifications than dr- IMRT. Fewer patients reported overall ≥ G3 acute toxicity with dr-IMRT. Most PRO symptoms and function changes had improved to baseline by 6 months, while sexual function had improved for men and women receiving dr-IMRT, it remained poor following sd-IMRT.

OC-0832 Organ Preservation in Early rectal Adenocarcinoma : 4-year results of the OPERA trial J. Gerard 1 , N. Barbet 2 , T. Pace-Loscos 3 , A. Sun Myint 4

1 Centre Antoine Lacassagne, Radiotherapy, NICE cedex 2, France; 2 Centre de Radiothérapie Bayard, Radiotherapy, Lyon Villeurbanne, France; 3 Centre Antoine Lacassagne, Biostatistics, NICE cedex 2, France; 4 Clatterbridge Cancer Center, Radiotherapy, Liverpool, United Kingdom Purpose or Objective The OPERA trial (NCT02505750)) was designed in 2014 to test the hypothesis that a Contact X Ray Brachytherapy 50kV (CXB) boost, preceding/following chemoradiotherapy (CRT) was able to increase the 3-year rate of organ preservation (OP),primary end point, for tumours of low-mid rectum. Materials and Methods Inclusion was : All age, cT2-T3 < 5cm Ø < 50% circumference, cN0-1 (< 8mm). Classification with MRI. All patients received neoadjuvant CRT (cape 45). Boost was randomised 1 :1 between Arm A : EBRT 9 Gy/fr. against Arm B : CXB 90 Gy/3 fr.Stratification separated T< 3cm (A1/B) vs ≥ 3cm (A2/B2) with CXB given first for B1. Response evaluation was made at week, 14, 20, 24 after treatment start using palpation, endoscopy , MRi. Results Between 5-2015/6-2020, 141 patients were included with intent to treat. Good balance between arms was observed : median age 69, Men : 87, Distal rectum :106, T2/T3 : 91/50, N0/1 : 106/35. Observance to all treatments was good in ≥ 94%. Median follow-up time (May 2021) was 38 months. Between week 14-24, a clinical complete (or near) response ncCR was observed in 44 patients in A (65.7%) vs 66 in B (94.3%) ; p<0.001. A TME surgery was performed in 39 patients (A : 26/B : 13).The OP rate was significantly increased in B (81%) vs A (59%) and still more in B1 vs A1 (97% vs 63%) (figure). No toxicity difference was seen between A and B (40, 4% grade 2-3) late, mild rectal bleeding was more frequent in B vs A (76% vs 23%). Bowel function was good in > 80% for both arms. These results will be updated with 4-year follow-up at time of the meeeting with additionnal data regarding MRI, Local excision and immunoscore.