What is the best approach for a patient with rectal cancer located 5 cm from the anal verge with suspected mesorectal invasion but no lymphadenopathy?

Management of Rectal Cancer 5 cm from Anal Verge with Suspected Mesorectal Invasion

For a patient with rectal cancer located 5 cm from the anal verge with suspected mesorectal invasion but no lymphadenopathy on MRI, neoadjuvant chemoradiotherapy followed by total mesorectal excision is the recommended approach.

Initial Assessment and Risk Stratification

• Pelvic MRI with dedicated rectal sequence is essential for accurate staging, including assessment of the tumor's relation to the anal verge, sphincter complex, mesorectal fascia (MRF), and evaluation of extramural vascular invasion (EMVI) 1
• For tumors located 5 cm from the anal verge (low rectal cancer), the risk of local recurrence is significantly higher compared to mid or upper rectal tumors 2
• Suspected mesorectal invasion (T3) with proximity to the mesorectal fascia represents a risk factor for local recurrence and requires neoadjuvant therapy 1

Treatment Recommendation

Neoadjuvant Therapy

• Neoadjuvant chemoradiotherapy is strongly recommended for low rectal cancer (5 cm from anal verge) with suspected mesorectal invasion to reduce local recurrence risk 1
• Long-course chemoradiation with concurrent fluoropyrimidine (continuous infusion 5-FU or oral capecitabine) is preferred over short-course radiotherapy for tumors with suspected mesorectal invasion 1
• Total neoadjuvant therapy (TNT) with long-course chemoradiation followed by chemotherapy should be offered to patients with low rectal cancer and risk factors for local recurrence 1

Surgical Approach

• Following neoadjuvant therapy, total mesorectal excision (TME) with adequate margins is the standard surgical approach 1, 3
• For tumors 5 cm from the anal verge, low anterior resection (LAR) with TME should be performed if adequate distal margin (1-2 cm) can be achieved with preservation of sphincter function 1, 3
• Abdominoperineal resection (APR) should be reserved for cases where the tumor directly involves the anal sphincter or when a margin-negative resection would result in loss of anal sphincter function 3

Response Assessment and Surgical Planning

• Clinical response assessment should be performed 8-12 weeks after completion of neoadjuvant therapy using digital rectal examination, proctoscopy, and MRI 1
• If complete clinical response is achieved, a "watch and wait" approach may be discussed as an alternative to surgery, particularly for patients who would otherwise require APR 1
• For partial response with significant downstaging, sphincter-preserving surgery should be reconsidered even if initially deemed impossible 1, 3

Special Considerations

• The quality of TME is a critical factor in reducing local recurrence and should be assessed postoperatively 1
• Postoperative adjuvant chemotherapy should be considered based on pathological staging and response to neoadjuvant therapy 1
• For patients with MSI-H or dMMR tumors, immunotherapy may be considered as part of the neoadjuvant approach 1

Common Pitfalls to Avoid

• Performing upfront surgery without neoadjuvant therapy for low rectal cancer with suspected mesorectal invasion increases local recurrence risk 2
• Inadequate imaging assessment before treatment decision can lead to understaging and suboptimal treatment selection 1
• Failure to allow adequate time (8-12 weeks) between completion of neoadjuvant therapy and surgery may result in suboptimal tumor response 4

Conclusion on Treatment Options

• Chemoradiotherapy followed by TME is the preferred approach for this patient with low rectal cancer (5 cm from anal verge) with suspected mesorectal invasion 1
• Low Anterior Resection (LAR) should be attempted if adequate distal margin can be achieved with preservation of sphincter function 3
• APR should only be performed if sphincter preservation is not feasible after neoadjuvant therapy 3