From the Guidelines
The desired minimum distal margin of resected rectal cancer is 1 cm (option a). This margin is considered adequate to ensure complete removal of the tumor while minimizing the risk of local recurrence, as supported by recent studies such as the AlaCaRT trial and the ACOSOG Z6051 trial, which found that a clear distal resection margin of ≥ 1mm is a key factor in achieving successful resection 1. For mid to upper rectal cancers, a 1 cm distal margin is often recommended to achieve oncologic clearance, while for very low rectal cancers, particularly those near the anal sphincter, this margin may be acceptable to preserve sphincter function while still maintaining oncologic principles. The distal margin is critical because inadequate margins increase the risk of local recurrence, while excessively wide margins may unnecessarily compromise functional outcomes, particularly regarding bowel control. Some studies suggest that age is not a predictor of postoperative morbidity on its own, and rectal cancer resection can be safely performed by laparoscopy also in elderly patients, with careful patient selection based on performance status and tumor characteristics 1.
Key points to consider in determining the desired minimum distal margin include:
- The type and location of the rectal cancer
- The patient's overall health and performance status
- The potential for sphincter preservation
- The risk of local recurrence and distant metastasis
- The impact of margin width on functional outcomes, such as bowel control. However, the most recent and highest quality study, the AlaCaRT trial, supports a minimum distal margin of 1 cm, which is the recommended standard for rectal cancer resection 1.
From the Research
Desired Minimum Distal Margin of Resected Rectal Cancer
The desired minimum distal margin of resected rectal cancer is a topic of ongoing debate.
- Studies have shown that a distal resection margin (DRM) of less than 1 cm may be sufficient in certain cases, particularly after preoperative chemoradiotherapy 2, 3, 4.
- However, other studies have found that a DRM of less than or equal to 1 cm may be associated with a higher risk of local recurrence and worse oncologic outcomes 5, 6.
- The generally accepted practice is to aim for a 2-cm DRM, but this may not always be possible, especially in cases where sphincter-sparing surgery is desired 3.
- The use of preoperative chemoradiotherapy may allow for a smaller DRM, as it can help to reduce the size of the tumor and minimize the risk of local recurrence 2, 4.
- Ultimately, the decision on the minimum distal margin should be made on a case-by-case basis, taking into account the individual patient's circumstances and the specific characteristics of the tumor 3, 5.
Key Findings
- A study published in 2019 found that a DRM of less than 1 cm was not associated with an increased risk of local recurrence or worse overall survival in patients with stage II or III rectal cancer who underwent preoperative chemoradiotherapy 2.
- A 2010 study suggested that a DRM of less than or equal to 1 cm may be sufficient in cases where preoperative chemoradiotherapy is used, but that a 2-cm margin is generally preferred 3.
- A 2022 systematic review and meta-analysis found that a DRM of less than or equal to 1 cm was associated with a higher risk of local recurrence, but that the overall survival rate was not significantly different from that of patients with a DRM of more than 1 cm 5.
- A 2001 study found that sphincter-sparing surgery with a DRM of less than or equal to 1 cm was not associated with an increased risk of local recurrence or worse disease-free survival in patients who underwent preoperative chemoradiotherapy 4.
- A 2017 study found that a distal margin of less than or equal to 1 mm was associated with worse oncologic outcomes, including a higher risk of local recurrence and worse disease-free survival 6.