Predictors for regional lymph node metastasis in T1 rectal cancer: a population-based SEER analysis.

Background: Local resection of early-stage rectal cancer significantly reduces perioperative morbidity compared with radical resection. Identifying patients at risk of regional lymph node metastasis (LNM) is crucial for long-term survival after local resection.

Methods: Patients after oncological resection of T1 rectal cancer were identified in the Surveillance, Epidemiology, and End Results register 2004-2012. Potential predictors of LNM and its impact on cancer-specific survival were assessed in logistic and Cox regression with and without multivariable adjustment.

Results: In total, 1593 patients with radical resection of T1 rectal cancer and a minimum of 12 retrieved regional lymph nodes were identified. The overall LNM rate was 16.3 % (N = 260). A low risk of LNM was observed for small tumor size (P = 0.002), low tumor grade (P = 0.002) and higher age (P = 0.012) in multivariable analysis. The odds ratio for a tumor size exceeding 1.5 cm was 1.49 [95 % confidence interval (CI) 1.06-2.13], for G2 and G3/G4 carcinomas 1.69 (95 % CI 1.07-2.82) and 2.72 (95 % CI 1.50-5.03), and for 65- to 79-year-old and over 80-year-old patients 0.65 (95 % CI 0.43-0.96) and 0.39 (95 % CI 0.18-0.77), respectively. Five-year cancer-specific survival for patients with LNM was 90.0 % (95 % CI 85.3-95.0 %) and for patients without LNM 97.1 % (95 % CI 95.9-98.2 %, hazard ratio = 3.21, 95 % CI 1.82-5.69, P < 0.001).

Conclusions: In this population-based analysis, favorable cancer-specific survival rates were observed in nodal-negative and nodal-positive T1 rectal cancer patients after primary radical resection. The predictive value of tumor size, grading and age for LNM should be considered in medical decision making about local resection.