This study evaluates whether an arginine-free diet combined with chemoradiotherapy can improve treatment outcomes in patients with locally advanced rectal cancer. Our previous study showed that an arginine-free diet is safe and may boost the body's immune response against tumors.
The study has two phases. The first phase (6 patients) tests the safety of the diet. The second phase (134 patients) randomly assigns participants to receive either the arginine-free diet plus standard chemoradiotherapy or standard chemoradiotherapy alone.
The arginine-free diet is provided as a liquid nutritional formula for 4 weeks. The main goal is to see if the diet increases the complete response rate (tumor disappearance). We will also evaluate survival outcomes, side effects, and quality of life.
Signed written informed consent prior to any study-related procedures.
Male or female, aged 18 to 80 years.
Locally advanced mid-low rectal cancer staged as cT3, cT4, or node-positive by rectal MRI.
ECOG performance status 0-1.
Stage I or IV rectal cancer.
Cognitive impairment or psychiatric disorders that interfere with understanding the study content.
Central nervous system or meningeal metastases.
Clinically symptomatic moderate or severe ascites (requiring therapeutic paracentesis within 2 weeks before starting study treatment; patients with minimal asymptomatic ascites on imaging may be enrolled).
Parallel
Arginine-Deprived Diet
Dietary supplementA nutritionally complete liquid formula providing 1978 kJ energy, 16.6 g protein, 22.2 g fat, 49.4 g carbohydrate, and 4.32 g dietary fiber per 100 g, with all essential amino acids except arginine. Participants receive the formula as a total diet replacement for 4 weeks during chemoradiotherapy. Daily intake is calculated based on standard body weight at 30 kcal/kg/day energy and 1.5 g/kg/day protein, typically 3.5-8.5 bottles per day (70 g/bottle, reconstituted in 300 mL warm water).
Short-Course Radiotherapy (SCRT)
RadiationShort-course radiotherapy delivered at 25 Gy in 5 fractions over 5 consecutive days during the first week of Cycle 2 (C2D1-C2D5, day 21-28 of the treatment schedule).
CAPOX + PD-1 Inhibitor
DrugCAPOX regimen (oxaliplatin 130 mg/m² IV on day 1 + capecitabine 1000 mg/m² oral twice daily on days 1-14) combined with PD-1 inhibitor (200 mg IV on day 1) every 3 weeks for 6 cycles.
Complete Response (CR) Rate (pCR + cCR)
Complete response rate is defined as the proportion of participants achieving either pathological complete response (pCR) or clinical complete response (cCR). pCR is defined as no residual tumor cells in the resected tumor tissue and regional lymph nodes. cCR is defined as no evidence of residual tumor in the primary lesion and regional lymph nodes (ycT0N0) after neoadjuvant treatment, assessed by rectal examination, endoscopy, pelvic MRI (T2WI/DWI), and serum CEA level.
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