Rectal Cancer Management
For rectal cancer, treatment is determined by clinical stage: early favorable tumors (cT1-2, N0) undergo surgery alone with total mesorectal excision (TME); intermediate-risk disease (most cT3, N+) requires preoperative short-course radiotherapy (25 Gy in 5 fractions) followed by immediate TME; and locally advanced tumors (cT3 with threatened circumferential resection margin, cT4) mandate preoperative chemoradiotherapy (50 Gy with concurrent 5-FU) followed by surgery 6-8 weeks later. 1
Diagnostic Workup
The initial evaluation must include:
- Digital rectal examination with rigid proctoscopy and biopsy for histopathological confirmation, with tumors ≤15 cm from the anal verge classified as rectal 2, 1
- Complete blood count, liver and renal function tests, carcinoembryonic antigen (CEA) level 2, 1
- Chest imaging (CT preferred over X-ray) and CT or MRI of abdomen/liver to assess for metastatic disease 2, 1
- Complete colonoscopy pre- or postoperatively to exclude synchronous lesions 2, 1
Local Staging: Critical for Treatment Selection
Accurate local staging determines whether neoadjuvant therapy is needed:
- Endoscopic ultrasound (EUS) for early tumors (cT1-T2) to assess depth of invasion 2, 1
- Rectal MRI for all other tumors to evaluate T stage, nodal status, circumferential resection margin (CRM) involvement, and extramural vascular invasion 2, 1
The MRI assessment of CRM status is particularly crucial—threatened or involved CRM mandates preoperative chemoradiotherapy rather than surgery alone. 1
Treatment Algorithm by Stage
Very Early Disease (T1 sm1-2, N0)
Local excision via transanal endoscopic microsurgery (TEM) is appropriate if the tumor meets all criteria: no vessel invasion, well or moderately differentiated, and complete resection with safe margins achieved 1. This approach avoids the morbidity of radical resection while maintaining oncologic outcomes in carefully selected patients.
Early Favorable Disease (cT1-2, some early cT3, N0)
Surgery alone using TME technique without neoadjuvant therapy is the standard approach 2, 1. These patients have sufficiently low risk of local recurrence that radiotherapy can be safely omitted. 2
Intermediate Risk (most cT3, N+)
Preoperative radiotherapy followed by immediate TME surgery is recommended 2, 1. The preferred regimen is:
- 25 Gy in 5 Gy fractions over one week, followed by immediate surgery 2, 1
- This short-course approach is convenient, simple, low-toxic, and reduces local recurrence rates 2
An alternative is 46-50 Gy in 1.8-2 Gy fractions with or without 5-FU, though this is more demanding without being more effective. 2
Locally Advanced Disease (cT3 with threatened CRM, cT4)
Preoperative chemoradiotherapy is mandatory for these high-risk tumors 2, 1:
- 50 Gy in 1.8 Gy fractions with concurrent 5-FU-based chemotherapy 2, 1
- Surgery delayed 6-8 weeks after completion to allow maximal tumor response 2, 1
- This approach can convert non-resectable tumors to resectable and may enable sphincter preservation 2
Preoperative treatment is always preferred over postoperative treatment when indicated, as it is more effective and less toxic. 2
Surgical Technique
Total mesorectal excision (TME) with sharp dissection is the standard surgical technique for all rectal cancers not amenable to local excision 2, 1, 3. This technique achieves local recurrence rates <10% and preserves quality of life. 2, 3
Key surgical principles:
- At least 12 lymph nodes must be examined for proper staging 2, 3
- Evaluation of proximal, distal, and circumferential resection margins is essential 2
- Low anterior resection should be employed whenever possible to preserve sphincter function 2
Postoperative Management
Adjuvant Chemotherapy
Adjuvant chemotherapy should be considered for stage III disease (and high-risk stage II), though evidence is less robust than for colon cancer 2, 1. Standard regimens include:
- 5-FU/leucovorin with oxaliplatin (FOLFOX) or irinotecan 4, 5
- Fluorouracil 400 mg/m² IV bolus on Day 1, followed by 2400-3000 mg/m² as continuous infusion over 46 hours every two weeks 4
Postoperative Chemoradiotherapy
Postoperative chemoradiotherapy is no longer routinely recommended but is reserved for specific high-risk situations if preoperative radiotherapy was not given 2, 1, 3:
- Positive circumferential margins
- Tumor perforation
- Other high risk of local recurrence features
The regimen is 50 Gy in 1.8-2.0 Gy fractions with concurrent 5-FU-based chemotherapy. 2, 3
Management of Local Recurrence
Patients with recurrence who did not receive prior radiotherapy should receive preoperative radiotherapy with concomitant chemotherapy 2, 3. Attempts at radical surgery should occur 6-8 weeks after radiotherapy completion. 2, 3
For previously irradiated patients, additional radiotherapy (external beam or intraoperative) can be attempted, though evidence is limited. 2
Metastatic Disease (Stage IV)
Resection of liver or lung metastases should be considered as part of curative-intent treatment in selected cases 2, 1. First-line palliative chemotherapy includes:
- 5-FU/leucovorin combined with oxaliplatin or irinotecan 2, 1
- Second-line chemotherapy for patients with maintained good performance status 2
Critical Pitfalls to Avoid
Do not proceed directly to surgery for locally advanced disease without neoadjuvant therapy—this significantly increases local recurrence risk and may compromise sphincter preservation opportunities. 2, 1
Do not rely on MRI staging after chemoradiotherapy—radiation-induced fibrosis, inflammatory infiltration, and vascular proliferation commonly cause overstaging (47% overstaged for T-level in one study), while residual cancer beneath normal-appearing mucosa can cause understaging. 6
Do not omit multidisciplinary team discussion—optimal outcomes require coordination among radiologists, surgeons, radiation oncologists, medical oncologists, and pathologists. 1, 7
Ensure adequate pathological examination—failure to examine at least 12 lymph nodes or assess circumferential margins compromises staging accuracy and treatment planning. 2, 3