Local Recurrence Risk After Horizontal Margin–Positive En Bloc Colorectal ESD

The systematic review and meta-analysis you are referencing provides an in-depth evaluation of the local recurrence risk after en bloc colorectal endoscopic submucosal dissection (ESD) with positive or indeterminate horizontal margins (HM1/x). Here is a detailed breakdown of the findings:

### Key Findings:

1. **Pooled Recurrence Rate**:

• Across 11 studies and 441 cases of HM1/x en bloc colorectal ESD, the pooled recurrence rate was found to be **4.3%**.
• This indicates that while the recurrence risk is elevated compared to cases with negative horizontal margins (HM0), the absolute risk remains relatively low.

2. **Nature of Recurrences**:

• Recurrence typically occurred at a **median of 14 months** post-procedure.
• Among the histologically characterized recurrences, the majority (13 out of 16) were **benign (dysplasia)** rather than invasive cancer.
• Invasive recurrences were associated with lesions initially classified as having invasive or high-grade dysplasia.

3. **Management of Recurrences**:

• Most benign recurrences were successfully treated with **repeat endoscopic procedures**.
• Invasive recurrences, however, required **surgical intervention**.

4. **Comparative Risk**:

• The recurrence risk was significantly higher in HM1/x cases compared to HM0 cases, with a pooled odds ratio of **8.04**.
• Despite this, the recurrence risk for noninvasive lesions was still relatively low, suggesting that the presence of HM1/x margins does not universally indicate a high recurrence risk.

5. **Implications for Surveillance**:

• The findings suggest that current surveillance recommendations, which are largely based on data from piecemeal endoscopic mucosal resection, may be overly cautious for en bloc ESD cases with HM1/x margins.
• Surveillance strategies could potentially be refined to balance early detection of recurrences with the avoidance of unnecessary interventions, especially for cases with low-risk pathology.

### Contextual Significance:

• The study highlights the importance of distinguishing between benign and invasive recurrences when managing patients with HM1/x margins after en bloc ESD.
• It also underscores the need for individualized surveillance protocols that take into account the specific pathology and recurrence risk of the lesion.

### Conclusion:

The local recurrence risk after en bloc colorectal ESD with positive or indeterminate horizontal margins (HM1/x) is low, at 4.3%, and is predominantly associated with benign dysplasia. Surveillance strategies may need to be adjusted to reflect this low absolute risk, especially for noninvasive lesions, while still ensuring the timely detection and management of any invasive recurrences.