Effects of tumor distance from anal verge on survival outcomes for rectal NENs and lymphatic metastasis risk score for colorectal NENs

Objective To explore whether the distance of rectal neuroendocrine neoplasms from the anal margin has an impact on the prognosis of patients and evaluate lymphatic metastases risk score for colorectal neuroendocrine neoplasms (NENs). Methods Clinical pathological and follow-up data of 71 patients identified as colorectal neuroendocrine neoplasms by pathology from July 2011 to July 2019 were carefully collected. Results Among 71 patients with colorectal NENs, most of the tumors were rectal NENs (62 cases). A total of 26 patients were in the presence of lymph node metastasis, and 44 patients had negative lymph nodes. Patients with lesions from the anal margin > 5 cm in rectum have a better prognosis ( P = 0.022). Tumor stage ( P = 0.034) and grade ( P = 0.001) were independent risk predictors of lymphatic metastases. We developed a lymphatic metastasis risk score for rectal NENs, and patients with the score ≥ 7.5 were more likely to develop lymph node metastases (area 0.958, 95% CI 0.903–1.000, P = 0.000) with a sensitivity of 72.2% and a specificity of 97.3%. Conclusion Patients with lesions from the anal margin > 5 cm and lymphatic metastasis risk score ≥ 7.5 should be treated actively.