Risk assessment of lymph node metastasis and comparison of treatment modalities for low-risk T1b colorectal cancer: a meta-analysis.

Background and aims: The uncertainty surrounding the risk of recurrence and metastasis in T1 colorectal cancer (CRC) with solely deep submucosal invasion (DSI, defined as T1b, submucosal invasion exceeding 1000 μm) as a high-risk factor has led to controversial treatment strategies. This meta-analysis aims to assess the risk of lymph node metastasis in T1 CRC patients presenting with a solitary risk factor of DSI. Furthermore, it compares the effectiveness and safety of endoscopic resection, surgery after endoscopic resection, and surgical resection in this context, offering valuable insights for clinical decision-making.

Methods: PubMed, Embase, and the Cochrane Library electronic databases were searched to identify available studies published up to November 30, 2024. Random- or fixed-effects models were applied in the meta-analyses. Heterogeneity and consistency were evaluated.

Results: The analysis encompassed 3331 cases of low-risk T1b CRC, pooled from 22 studies. The lymph node metastasis (LNM) rate of low-risk T1b CRC is 2.5% (95% CI 1.3-3.8%). Patients of this kind treated with endoscopic resection, surgery after endoscopic resection, or surgical resection alone do not differ statistically significantly in terms of recurrence rates (P = 0.28) or disease-specific survival (DSS) rate (P = 0.66). In addition, R0 resection could be achieved with endoscopic resection in the majority of patients, without serious adverse events reported in documented cases.

Conclusions: For patients with early-stage colorectal cancer presenting as DSI and devoid of other risk factors, treatment should be individualized. In such cases, given the low LNM rate, appropriately expanding the indications for endoscopic treatment and implementing rigorous follow-up post-endoscopic resection may represent a feasible strategy for selected patients, especially when balancing risks of unnecessary surgery. Otherwise, surgical resection remains the preferred treatment.