Multimodality treatment including surgery and radiotherapy is the current standard of care in locally advanced rectal cancer. Most clinical trials comparing short course radiotherapy (SCRT) with long course chemoradiotherapy(LCRT) did not find significant differences in oncological outcomes and short-term outcomes even though some debates. Recently, Stockholm III trial comparing SCRT plus delayed surgery with SCRT plus immediate surgery and LCRT demonstrated no differences with respect to short-term outcomes such as complications, mortality, and acute toxicity. However, overall quality of life (QoL) after curative treatment for rectal cancer is still major concern in both SCRT and LCRT. Furthermore, daily hospital visits for 5 weeks may be the cause of the increase of total medical cost due to indirect medical expense in patients with LCRT, especially in rural area. SCRT plus chemotherapy followed by delayed surgery may have the possibility of reducing total hospital costs as well as increasing QoL by proving non-inferiority in terms of perioperative outcomes. The present prospective single-arm phase 2 trial was designed to validate the efficacy, quality of life and cost effectiveness of preoperative short-course radiotherapy plus XELOX chemotherapy followed by delayed surgery for high-risk rectal cancer patient based on magnetic resonance imaging.

Inclusion Criteria:

1. High-risk patients of rectal cancer on pretreatment MRI using the following risk stratification system Location of the lower part of the tumor is measured below less than 10 cm on the anal verge and lower part of the tumor is located below the lower limit of the peritoneal reflection.

   If there is more than one, classify as a high risk group Positive CRM threatening: 5mm ≦ Extramural depth Positive EMVI.

   cN2: Positive Lateral pelvic LN metastasis

2. Between 19 and 80 years of age;

3. Satisfactory performance status: ECOG≦2

4. American Society of Anesthesiologists (ASA) physical status classification system class I~III

5. Adequate hematologic function: white blood cell(WBC) counts≥4,000/mm3, neutrophils counts ≥ 1,500/mm3, platelet counts ≥ 100,000/µL, hemoglobin ≥ 9g/L;

6. Adequate renal function: creatinine ≤ 1.5×upper normal limit

Exclusion Criteria:

1. The evidence of relapse of distant metastasis
2. Receiving treatment of other anti-cancer drug or methods
3. Patients have low compliance and are not able to complete the entire trial
4. Presence of uncontrolled life-threatening diseases
5. cT4 with infiltration of anterior organ on pretreatment MRI
6. cT4 with infiltration of internal or external anal sphincter on pretreatment MRI