Abstract
Rectal neuroendocrine tumors (r-NETs) are rare tumors with overall good prognosis after complete resection. However, there is no consensus on the extension of lymphadenectomy or regarding contraindications to extensive resection. In this study, we aim to identify predictive factors that correlate with nodal metastasis in patients affected by G1–G2 r-NETs. A retrospective analysis of G1–G2 r-NETs patients from eight tertiary Italian centers was performed. From January 1990 to January 2020, 210 patients were considered and 199 were included in the analysis. The data for nodal status were available for 159 cases. The nodal involvement rate was 9%. A receiver operating characteristic (ROC) curve analysis was performed to identify the diameter (>11.5 mm) and Ki-67 (3.5%), respectively, as cutoff values to predict nodal involvement. In a multivariate analysis, diameter > 11.5 mm and vascular infiltration were independently correlated with nodal involvement. A risk scoring system was constructed using these two predictive factors. Tumor size and vascular invasion are predictors of nodal involvement. In addition, tumor size > 11.5 mm is used as a driving parameter of better-tailored treatment during pre-operative assessment. Data from prospective studies are needed to validate these results and to guide decision-making in r-NETs patients in clinical practice.
Highlights
Rectal neuroendocrine tumors (r-NETs) represent a heterogeneous group of rare malignancies that account for up to 13.7% of all neuroendocrine tumors (NETs) [1]
Patients with neuroendocrine carcinoma (NEC) grade 3 (G3), mixed adenoneuroendocrine carcinoma (MANEC), or no evidence of r-NETs on pathology revision were excluded from the analysis
Of the 210 patients considered for the analysis, eleven patients were excluded, ten because they were affected by rectal NEC and one for being affected by MANEC
Summary
Rectal neuroendocrine tumors (r-NETs) represent a heterogeneous group of rare malignancies that account for up to 13.7% of all neuroendocrine tumors (NETs) [1]. The age-adjusted incidence of r-NETs has increased about sixfold over the last. 40 years, probably due to the increased use of endoscopic procedures for colorectal cancer screening [2]. R-NETs typically appear as single smooth yellowish polypoid lesions that originate from deeper layers of the mucosa and protrude from the mucosal surface into the lumen of the rectum without surface distortion [3,4]. Rectal lesions less than 10 mm in size typically show an indolent course, with the nodal involvement incidence ranging from 1% to 10%, a high rate of curative resection, and 5-year survival of 98 to 100%. In the case of r-NETs 10 mm to 20 mm and larger than 20 mm in size, the reported incidence of nodal involvement increases to 30%
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