What is the recommended treatment approach for patients undergoing low anterior resection (LAR) for rectal cancer?

Treatment Approach for Low Anterior Resection in Rectal Cancer

Total mesorectal excision (TME) with low anterior resection should be the preferred surgical approach for rectal cancer whenever possible, as it provides low local recurrence rates (<10%) and good quality of life. 1

Preoperative Assessment and Staging

• Complete clinical evaluation including rectal examination, rigid proctoscopy with biopsy, complete blood count, liver and renal function tests, CEA, and imaging (chest X-ray, CT/MRI/ultrasound of liver) 1
• Endoscopic ultrasound or rectal MRI is recommended to select patients for preoperative treatment 1
• Complete colonoscopy should be performed either pre- or postoperatively 1

Preoperative Treatment

• Preoperative radiotherapy (e.g., 25 Gy, 5 Gy/fraction followed by immediate surgery) reduces local recurrence rate 1
• Preoperative chemoradiotherapy (50 Gy, 2 Gy/d + 5-FU continuous infusion during the first and fifth week) is preferred over postoperative chemoradiotherapy due to decreased toxicity 1
• Surgery should be performed 6-8 weeks after completion of chemoradiotherapy 1

Surgical Approach Based on Tumor Location

• For lesions in the mid to upper rectum, low anterior resection is the treatment of choice 1, 2
• For low rectal lesions, either abdominoperineal resection or coloanal anastomosis is required 1
• For small tumors (T1-T2) within 8 cm of the anal verge and limited to 30% of the rectal circumference, transanal excision may be considered 1

Technical Considerations for Low Anterior Resection

• Total mesorectal excision technique is strongly recommended as it gives a low local recurrence rate (<10%) 1
• A safe margin between the lower end of the tumor and the rectal stump must be greater than or equal to 2 cm 2
• At least 12 lymph nodes should be examined for proper staging 1
• For tumors of the lower third of the rectum, excision of the entire mesorectum reduces the risk of locoregional recurrence 2

Postoperative Treatment

• Postoperative radiotherapy (50 Gy, 1.8-2.0 Gy/fraction) with concomitant 5-FU based chemotherapy is recommended in patients with positive circumferential margins, perforation in the tumor area, or other high-risk features if preoperative radiotherapy has not been given 1
• Similar to colon cancer stage III (and 'high-risk' stage II), adjuvant chemotherapy can be provided, though scientific support for sufficient effect is less robust 1

Management of Advanced Disease

• For fixed tumors or local recurrence (if radiotherapy was not given initially), preoperative radiotherapy with or without concomitant chemotherapy should be administered 1
• Attempts at radical surgery should take place 4-8 weeks after radiotherapy 1
• For disseminated disease, treatment may include surgery of resectable liver or lung metastases in selected cases 1

Follow-up Protocol

• History and rectosigmoidoscopy every 6 months for 2 years 1
• History and colonoscopy with resection of colonic polyps every 5 years 1
• Clinical, laboratory, and radiological examinations should be restricted to patients with suspicious symptoms 1

Potential Complications and Functional Outcomes

• Preoperative chemoradiation may result in increased operative time, blood loss, and pelvic abscess formation but does not increase the rate of anastomotic leaks or length of hospital stay 3
• Patients undergoing ultralow anterior resection (ULAR) with coloanal anastomosis often experience significant bowel dysfunction, with 70.6% still having major low anterior resection syndrome (LARS) at 36 months post-surgery 4
• Risk factors for major LARS include older age (>70), male sex, ultralow anterior resection, and chemoradiation therapy 4

Survival and Recurrence Outcomes

• With proper TME technique, the 5-year actuarial overall survival rate for patients undergoing curative resection can exceed 80%, with local recurrence rates of approximately 10% 3
• Low anterior resection has been shown to provide equal or better outcomes compared to abdominoperineal resection for middle and low rectal cancers, with 5-year survival rates of 79.8% vs. 78.7% and pelvic recurrence rates of 8.9% vs. 13.5% 5