What is the role of surgery in the treatment of anal cancer?

Role of Surgery in Anal Cancer Treatment

Surgery in anal cancer is primarily reserved for salvage treatment after failure of chemoradiation therapy, as the standard of care for most anal cancers is chemoradiation with the goal of preserving anal function and avoiding permanent colostomy. 1

Primary Treatment Approach

• Chemoradiation (CRT) with at least 45 Gy radiation combined with 5-fluorouracil (5-FU) and mitomycin C (MMC) is the standard first-line treatment for stage II or higher anal canal tumors 1
• Local excision alone is appropriate only for well-differentiated T1 anal margin tumors (<2 cm) without evidence of nodal involvement 1
• The primary aim of treatment is locoregional control with good quality of life and avoidance of permanent stoma 1

Surgical Indications in Anal Cancer

Primary Surgical Treatment

• Surgery as primary treatment is limited to small (T1) well-differentiated cancers of the anal margin where sphincter function will not be compromised 1
• Until the mid-1980s, abdominoperineal resection (APR) was the standard treatment but was associated with high local failure rates (up to 50%) and 5-year survival rates of only 50-70% 1

Salvage Surgery

• Patients with locally persistent, progressive, or recurrent disease after chemoradiation should be considered for surgical salvage (Level of Evidence I, A) 1
• Salvage surgery typically involves abdominoperineal resection (APR) as the minimum procedure required 1
• Achievement of negative resection margins is crucial for successful outcomes 1
• For some patients with more extensive disease, posterior or total pelvic exenteration may be required 1

Preoperative Considerations for Salvage Surgery

• Histological confirmation of residual or recurrent disease is mandatory before proceeding to radical surgery 1
• Preoperative local staging with MRI is essential 1
• CT scan of thorax and abdomen or PET/CT is advised to rule out distant metastases 1
• Surgery should preferably be carried out in institutions with experience in multi-visceral resections 1

Surgical Procedures and Techniques

• A very small proportion of patients may be treated by local resection for limited recurrence 1
• Most patients require at least an abdominoperineal excision 1
• Salvage operations for anal cancer involve wider perineal resection than what is done for rectal cancer 1
• Perineal reconstruction with musculocutaneous flaps (such as vertical rectus abdominis musculocutaneous flaps) is generally recommended to reduce complication rates 1, 2
• Multi-visceral resection is often necessary, requiring collaboration with urologists, gynecologists, and plastic surgeons 1, 3

Outcomes of Salvage Surgery

• Salvage surgery can achieve local pelvic control in approximately 60% of cases 1
• 5-year survival rates after salvage surgery range from 30-60% 1, 2
• Smaller recurrences (rpT2) have better outcomes with no recurrences reported in some series 3
• Patients who initially received adequate radiation doses (≥55 Gy) have better survival after salvage surgery 4

Complications and Challenges

• Surgery in previously irradiated areas carries substantial risk of post-operative complications 1
• Perineal wound complications are particularly common, occurring in 36-57% of cases 3, 2
• Wound breakdown can lead to prolonged healing times (median 7 months in some studies) 5
• Use of musculocutaneous flaps for reconstruction significantly reduces wound complications 2

Special Considerations

• Persistent or progressive disease in the inguinal lymph nodes should be considered for radical groin dissection 1
• Pre- or post-operative irradiation may be considered for inguinal disease, depending on the dose distribution from the definitive CRT 1
• Higher radiation boost doses during initial CRT may decrease the need for salvage APR 6
• Patients with poorly differentiated tumors or positive resection margins after salvage surgery have worse outcomes 5

Follow-up After Treatment

• Clinical response should be assessed 6-8 weeks after completion of chemoradiation 1
• Good partial regression can be managed by close follow-up for 3-6 months to confirm complete regression before considering surgery 1
• Patients in complete remission should be evaluated every 3-6 months for 2 years, then every 6-12 months until 5 years 1

In conclusion, while chemoradiation remains the cornerstone of anal cancer treatment, surgery plays a vital role in salvage therapy for persistent or recurrent disease, offering a chance for long-term survival despite significant morbidity.