Oral B-Complex Vitamin (B6, B9 and B12) Prevents Low Anterior Resection Syndrome in Rectal Cancer Patients With Hyperhomocysteinemia - NCT07928180

Sponsor: Qilu Hospital of Shandong University Conditions: Low Anterior Resection Syndrome, Hyperhomocysteinemia, Rectal Cancer The goal of this clinical trial is to investigate if taking Oral B-Complex Vitamin (B6, B9 and B12) can help prevent low anterior resection syndrome (LARS) in rectal cancer patients with hyperhomocysteinemia after sphincter-preserving surgery for rectal cancer. LARS is a group of bowel problems that can occur after rectal cancer surgery, including frequent bowel movements, an urgent need to have a bowel movement, constipation, and loss of bowel control. Our previous research suggests that hyperhomocysteinemia increased the occurrence of LARS. Folic acid, vitamin B6 and vitamin B12 are a safe, widely used way to treat hyperhomocysteinemia. The main questions this study aims to answer are: * Does taking Oral B-Complex Vitamin (B6, B9 and B12) lower the rate of LARS 6 months after surgery? * How does this treatment affect internal anal sphincter (IAS) function? Researchers will compare Oral B-Complex Vitamin (B6, B9 and B12) with a placebo (a look-alike tablet that contains no vitamins) to see if Oral B-Complex Vitamin (B6, B9 and B12) can help prevent LARS. Participants will: * Take B-Complex Vitamin (B6, B9 and B12) every day for 6 months * Visit the clinic twice ( 3 months and 6 months after surgery) for checkups and tests * Complete the LARS score questionnaire 6 months after surgery Low anterior resection syndrome (LARS) is a cluster of bowel dysfunction symptoms after sphincter-preserving surgery for rectal cancer, including incontinence, urgency, and frequent bowel movements. The Chinese Expert Consensus on the Diagnosis and Treatment of LARS (2025 edition) reports an incidence of 69.8% at 3 months and 62.3% at 6-9 months after low anterior resection. LARS may persist for years and substantially impair quality of life. LARS is multifactorial, involving reduced rectal capacity and compliance, internal anal sphincter dysfunction and nerve injury. No drug or treatment is currently available to prevent LARS. Hyperhomocysteinemia (HHcy) is defined as a serum homocysteine (Hcy) level above 15 μmol/L. The pooled prevalence of hyperhomocysteinemia (Hcy \>15 μmol/L) in China was 25.9%. The prevalence of hyperhomocysteinemia is higher in cancer patients. Hyperhomocysteinemia increases the risk of various cardiovascular and cerebrovascular diseases, including coronary heart disease and stroke. Our preliminary data showed that, in a single-center cohort of 530 patients who underwent low anterior resection for rectal cancer at Qilu Hospital of Shandong University between December 2023 and December 2025, hyperhomocysteinemia was present in 105 of 205 patients with LARS (51.2%) and in 95 of 325 patients without LARS (29.2%). This suggests hyperhomocysteinemia may be a risk factor of LARS. In a Sprague-Dawley rat model of low anterior resection, hyperhomocysteinemia shortened colonic transit time and increased fecal water content. Postoperative supplementation with folic acid, vitamin B6 and vitamin B12 lowered serum Hcy and reversed these changes. In our prospective single-arm pilot study, 80 patients who met the same eligibility criteria received Oral B-Complex Vitamin treatment. No adverse events were observed. After 6 months, majority of patients' Hcy levels returned to normal. LARS occurrence was much lower than 62.3%.