Impact of adequate lymph nodes dissection on survival in patients with stage I rectal cancer

Background and Aims: The NCCN guidelines recommended an assessment of >= 12 lymph nodes (LN) as an adequate LN dissection (LND) for rectal cancer (RC). However, the impact of adequate LND on survival in stage I RC patients remained unclear. Thus, we aimed to compare the survival between stage I RC patients with adequate and inadequate LND. Methods: A total of 1,778 stage I RC patients in the SEER database from 2010 to 2017 treated with radical proctectomy were identified. The association between >= 12 LND and survival was examined using the multivariate Cox regression and the multivariate competing risk model referenced to < 12 LND. Results: Stage I RC patients with >= 12 LND experienced a significantly lower hazard of cancer-specific death compared with those with < 12 LND in both multivariate Cox regression model (adjusted HR [hazard ratio], 0.44, 95% CI, 0.29-0.66; P < 0.001) and the multivariate competing risk model (adjusted subdistribution HR [SHR], 0.45, 95% CI, 0.30-0.69; P < 0.001). Further, subgroup analyses performed by pT stage. No positive association between = 12 LND and survival was found in pT1N0 RC patients (adjusted HR: 0.62, 95% CI, 0.32-1.19; P = 0.149; adjusted SHR: 0.63, 95%CI, 0.33-1.20; P = 0.158), whereas a positive association between >= 12 LND and survival was found in pT2N0 RC patients (adjusted HR: 0.35, 95%CI, 0.21-0.58; P < 0.001; adjusted SHR: 0.36, 95%CI, 0.21-0.62; P < 0.001). Conclusions: The long-term survival benefit of adequate LND was not found in pT1N0 but in pT2N0 RC patients, which suggested that pT2N0 RC patients should be treated with adequate LND and those with inadequate LND might need additional therapy.