What is the completeness of resection in Low Anterior Resection (LAR)?

From the Guidelines

Completeness of resection in Low Anterior Resection (LAR) is crucial for optimal oncologic outcomes, and a complete resection should achieve negative circumferential resection margins (CRM) and distal margins, with a goal of at least 1-2 cm distal margin when possible, as recommended by the international collaboration on cancer reporting (ICCR) in 2022 1.

Key Considerations for Completeness of Resection

• Total mesorectal excision (TME) is the standard surgical technique, requiring removal of the entire mesorectum with an intact mesorectal fascia to ensure complete removal of potential tumor deposits, as described in the ICCR guidelines 1.
• The optimal plane of dissection is the mesorectal fascia, and any deviation from this plane can lead to incomplete resection and increased risk of local recurrence, as shown in Table 2 of the ICCR guidelines 1.
• Intraoperative assessment of margins may be performed with frozen section analysis when margins appear close, and pathological evaluation should include assessment of the completeness of the mesorectal excision, status of the CRM, and distal margin, as recommended by the ICCR guidelines 1.
• Preoperative staging with MRI helps determine the extent of disease and plan appropriate surgical approach, and in cases where complete resection appears challenging due to locally advanced disease, neoadjuvant chemoradiotherapy should be considered to downstage the tumor and increase the likelihood of complete resection.

Importance of Complete Resection

• Incomplete resection significantly increases the risk of local recurrence and reduces overall survival, as shown in previous studies 1.
• The quality of surgical technique for colonic cancer, evaluating the plane of mesocolic excision, has been shown to predict outcomes, with surgery in the mesocolic plane associated with a lower rate of local recurrence and better survival when compared to surgery in the muscularis propria plane, as described in the ICCR guidelines 1.
• Complete mesocolic excision, where surgery occurs in the mesocolic plane with a high vascular ligation, is associated with better plane of surgery and higher lymph node yield, although the effect of the high ligation on long term outcomes is uncertain and subject to further study, as noted in the ICCR guidelines 1.

From the Research

Completeness of Resection in Low Anterior Resection (LAR)

• The completeness of resection in LAR is a critical factor in determining the outcome of rectal cancer treatment 2.
• Studies have shown that the use of preoperative chemoradiotherapy can improve the completeness of reection by downstaging the tumor 3, 4.
• The addition of oxaliplatin to capecitabine-based chemoradiotherapy has been shown to increase the pathologic complete remission rate without significantly increasing adverse effects or impairing postoperative recovery 5.
• However, the use of oxaliplatin has also been associated with increased toxicity, particularly grade 3 or 4 diarrhea 6.
• The surgical end points, including complete pathologic response, sphincter-sparing surgery, and surgical downstaging, have been shown to be similar between different chemoradiotherapy regimens, including capecitabine and oxaliplatin-based regimens 6.

Factors Affecting Completeness of Resection

• The technical aspects of the surgical procedure, including the use of total mesorectal excision (TME), can affect the completeness of resection 2.
• The experience and skill of the surgeon can also impact the completeness of resection 2.
• The use of neoadjuvant chemoradiotherapy can downstage the tumor, making it easier to achieve a complete resection 3, 4.

Outcomes of Complete Resection

• Complete resection has been shown to improve local control and disease-free survival in patients with rectal cancer 4.
• The use of preoperative chemoradiotherapy has been shown to improve the completeness of resection and overall survival in patients with locally advanced rectal cancer 3, 4.
• However, the long-term effectiveness of different chemoradiotherapy regimens in preventing metastasis and recurrence is still unclear 5.