Objective To evaluate the efficacy of an intensified neoadjuvant therapy regimen in improving outcomes for stage Ⅱ/Ⅲ rectal cancer patients with high-risk factors.Methods A total of 123 stage Ⅱ/Ⅲ rectal cancer patients with high-risk factors were enrolled and divided into two groups:neoadjuvant mFOLFOX6 concurrent chemoradiotherapy(CRT)group(mFOLFOX6+CRT,n=60)and single-agent 5-fluorouracil(5-FU)concurrent CRT group(5-FU+CRT,n=63).The mFOLFOX6+CRT group received two cycles of mFOLFOX6 concurrent with pelvic conventional fractionated radiotherapy,while the 5-FU+CRT group received 5-FU 225 mg/(m2·d)continuous intravenous infusion on days 1-5 weekly for five weeks during radiotherapy.Both groups underwent total mesorectal excision(TME)5-12 weeks after completing neoadjuvant therapy,followed by adjuvant chemotherapy 4 weeks post-surgery.Pathologic complete response(pCR)rate,tumor downstaging rate,R0 resection rate,local recurrence,distant metastasis,overall survival(OS),and adverse events were compared between groups.Results The mFOLFOX6+CRT group showed significantly higher pCR rate(20.8%vs 5.9%,P=0.026),tumor downstaging rate(77.4%vs 60.8%,P=0.067),and 3-year OS(71.7%vs 67.4%,P=0.557)compared to the 5-FU+CRT group.The mFOLFOX6+CRT group also had lower 3-year local recurrence(3.8%vs 9.8%,P=0.265),distant metastasis(17.0%vs 33.5%,P=0.044),and RO resection rates(88.7%vs 92.2%,P=0.742).After adjusting for imbalances,the mFOLFOX6+CRT group was more likely to achieve pCR(OR=7.38,95%CI was 1.72-31.72,P=0.007).There were no significant differences in adverse events or surgical complications between groups(P>0.05).Conclusion Compared to standard 5-FU concurrent CRT,neoadjuvant mFOLFOX6 concurrent CRT significantly improves short-term outcomes(pCR rate)and shows potential long-term benefits in reducing distant metastasis for stageⅡ/Ⅲ rectal cancer patients with high-risk factors.