Neoadjuvant S‐1 and oxaliplatin plus bevacizumab therapy for high‐risk locally advanced rectal cancer: A prospective multicenter phase <scp>II</scp> study

Aim We report the short/mid-term results of surgery for high-risk locally advanced rectal cancer (LARC) after neoadjuvant chemotherapy (NAC, four courses S-1 + oxaliplatin+ bevacizumab) without radiotherapy with primary aim ypT0-2. Methods High-risk LARC was defined as cT4b, mesorectal fascia (MRF) ≤1 mm (MRF+), or lateral lymph node metastasis (cLLN+) on high-resolution MRI. The planned 32 cases from April 2018 to December 2021 were all included. Results There 10 patients at cT4b (31.2%), 26 MRF+ (81.3%), and 22 cLLN+ (68.8%). Thirteen (40.6%) underwent NAC a colostomy stenosis. completed in (81.2%) cases. Grade 3 higher adverse events occurred six (18.7%). One patient developed progressive disease (3.2%). Eleven ycT0-3MRF-LLN- (34.3%). Curative-intent performed 31, sphincter-preserving 20, abdominoperineal resection nine, total pelvic exenteration two, dissection 24. Two had R1/2 (6.4%). A postoperative complication rate 3.2%. Pathological complete response ypT0-2 rates 12.9% 45.1%. Three-year disease-free survival (3yDFS) ypT ≥3 81.2%, 46.6% (p = 0.061), 3-year local recurrence (3yLR) 0%, 48.8% 0.015). 3yDFS ycT4/MRF+/LLN+ 87.5%, 48.0% 0.031) 3yLR 42.8% 0.045). Conclusion yielded clinically significant effect about half patients. If alone is ineffective, should be added, even if extended intended.