Neoadjuvant Chemoradiation Followed by Surgery
For a patient with rectal cancer located 5 cm from the anal verge with no lymph node involvement, neoadjuvant chemoradiation followed by total mesorectal excision (TME) is the best next step. 1
Rationale for Neoadjuvant Therapy
This tumor is classified as low rectal cancer (≤5 cm from anal verge), and even without documented lymph node involvement, the location itself represents a risk factor for local recurrence that warrants neoadjuvant treatment. 2
- Pelvic MRI staging is critical to assess mesorectal fascia involvement, extramural vascular invasion (EMVI), and T-stage, which will determine the exact neoadjuvant approach. 1
- For low rectal cancers at 5 cm from the anal verge with suspected mesorectal invasion (T3), neoadjuvant chemoradiotherapy significantly reduces local recurrence risk. 1
- Long-course chemoradiation with concurrent fluoropyrimidine (continuous infusion 5-FU or oral capecitabine 825 mg/m² twice daily, 5 days per week) is the preferred regimen. 2, 1
- The radiation dose should be 45.0-50.4 Gy over 25-28 fractions, with consideration for an additional 5.4 Gy/3 fractions boost to the tumor. 2
Surgical Approach After Neoadjuvant Therapy
Following neoadjuvant chemoradiation, surgery should be performed 8-12 weeks after completion to allow for maximal tumor response. 2, 1
Low Anterior Resection (LAR) vs Abdominoperineal Resection (APR)
- LAR with TME should be attempted if adequate distal margin (1-2 cm) can be achieved with preservation of sphincter function after tumor downstaging from neoadjuvant therapy. 3, 1
- For tumors at exactly 5 cm from the anal verge, neoadjuvant therapy often allows sufficient tumor regression to permit sphincter-preserving surgery. 4
- APR should be reserved only for cases where the tumor directly involves the anal sphincter or when margin-negative resection would result in loss of sphincter function. 1, 5
- Recent evidence shows patients treated with APR have worse local control, overall survival, and quality of life compared to LAR. 5
Critical Technical Points
- Total mesorectal excision (TME) extending 4-5 cm below the distal tumor edge is mandatory regardless of whether LAR or APR is performed. 2, 3
- The circumferential resection margin (CRM) must be negative (>1 mm from tumor). 2
- A distal bowel wall margin of 1-2 cm is acceptable for distal rectal cancers and must be confirmed tumor-free by frozen section. 2
- Post-treatment lymph node status is the most important prognostic factor for disease-free survival after neoadjuvant therapy. 6
Why Not Immediate Surgery?
Proceeding directly to LAR or APR without neoadjuvant therapy would be inappropriate because:
- Low rectal cancers have higher local recurrence rates without neoadjuvant treatment. 1
- Neoadjuvant therapy may convert an APR candidate to a sphincter-preserving LAR candidate, dramatically improving quality of life. 4
- The lateral resection margin status significantly affects disease-free survival, and neoadjuvant therapy improves margin negativity. 6, 7
Post-Neoadjuvant Assessment
- Clinical response should be assessed with digital rectal examination, proctoscopy, and MRI 8-12 weeks after completing neoadjuvant therapy. 1
- If complete clinical response is achieved, a "watch and wait" approach may be discussed, though this is typically reserved 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