Management of Low Rectal Cancer

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
Suspected mesorectal invasion (T3) with proximity to the mesorectal fascia represents a risk factor for local recurrence and requires neoadjuvant therapy 1, 2

Neoadjuvant chemoradiotherapy is strongly recommended for low rectal cancer (5 cm from anal verge) with suspected mesorectal invasion to reduce local recurrence risk 1, 2
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, 3
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

Following neoadjuvant therapy, total mesorectal excision (TME) with adequate margins is the standard surgical approach 2, 4
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 5, 4
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 4

Clinical response assessment should be performed 8-12 weeks after completion of neoadjuvant therapy using digital rectal examination, proctoscopy, and MRI 2, 3
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 2, 4

The quality of TME is a critical factor in reducing local recurrence and should be assessed postoperatively 2
Postoperative adjuvant chemotherapy should be considered based on pathological staging and response to neoadjuvant therapy 1, 2
For patients with MSI-H or dMMR tumors, immunotherapy may be considered as part of the neoadjuvant approach 1, 6

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, 2