Background Preoperative(chemo)radiotherapy has been widely used as an effective treatment for locally ad-vanced rectal cancer(LARC),leading to a significant reduction in pelvic recurrence rates.Because early administration of intensive chemotherapy for LARC has more advantages than adjuvant chemotherapy,total neoadjuvant therapy(TNT)has been introduced and evaluated to determine whether it can improve tumor response or treatment outcomes.This study aims to investigate whether short-course radiotherapy(SCRT)followed by intensive chemotherapy improves oncologic out-comes compared with traditional preoperative long-course chemoradiotherapy(CRT).Methods A multicenter randomized phase Ⅱ trial involving 364 patients with LARC(cT3-4,cN+,or presence of extramural vascular invasion)will be con-ducted.Patients will be randomly assigned to the experimental or control arm at a ratio of 1:1.Participants in the ex-perimental arm will receive SCRT(25 Gy in 5 fractions,daily)followed by four cycles of FOLFOX(oxaliplatin,5-fluoro-uracil,and folinic acid)as a neoadjuvant treatment,and those in the control arm will receive conventional radiotherapy(45-50.4 Gy in 25-28 fractions,5 times a week)concurrently with capecitabine or 5-fluorouracil.As a mandatory surgical procedure,total mesorectal excision will be performed 2-5 weeks from the last cycle of chemotherapy in the experimen-tal arm and 6-8 weeks after the last day of radiotherapy in the control arm.The primary endpoint is 3-year disease-free survival,and the secondary endpoints are tumor response,overall survival,toxicities,quality of life,and cost-effectiveness.Discussion This is the first Korean randomized controlled study comparing SCRT-based TNT with traditional preopera-tive LC-CRT for LARC.The involvement of experienced colorectal surgeons ensures high-quality surgical resection.SCRT followed by FOLFOX chemotherapy is expected to improve disease-free survival compared with CRT,with potential advan-tages in tumor response,quality of life,and cost-effectiveness.
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