Prognostic Factors in Neuroendocrine Neoplasms of the Rectum

Neuroendocrine neoplasms (NENs) of the rectum (rNEN) are a rare and heterogeneous group of tumors that can vary greatly in their biological behavior, from benign to highly aggressive. While small and well-differentiated tumors can often be handled endoscopically and still face a very good prognosis, tumor size, and grade, as well as lymph node and distant metastasis, are known risk factors for impaired prognosis. This study aimed at the identification of further prognostic factors in rNEN.

A retrospective analysis of patients treated for rNEN at the ENTES Center of Excellence at Charité-Universitätsmedizin, including n = 121 patients, was performed to identify risk factors for recurrence, progression, and impaired outcome.

Progression-free survival (PFS) and overall survival (OS) differed significantly according to tumor grade (p < 0.001). In rNET patients undergoing surgery, the Ki-67 index and distant metastases were independent risk factors for shorter PFS. Among stage I rNETs, 10 patients developed disease recurrence, associated with lymphatic invasion (1.9% vs. 30.0%, p = 0.008) and higher Ki-67 values (2 (1-6) vs. 2 (1-16), p = 0.054).

Tumor grade and presence of metastases represent important predictive factors in rNEN. Notably, even small, early-stage rNETs can harbor a risk of recurrence when unfavorable pathological features are present, highlighting the importance of tailored, risk-adapted surveillance strategies to optimize patient outcomes.