Grade is a Dominant Risk Factor for Metastasis in Patients with Rectal Neuroendocrine Tumors

• Published in: Annals of surgical oncology Vol. 27; no. 3; pp. 855 - 863
• Main Authors: Folkert, Ian W., Sinnamon, Andrew J., Concors, Seth J., Bennett, Bonita J., Fraker, Douglas L., Mahmoud, Najjia N., Metz, David C., Stashek, Kristen M., Roses, Robert E.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.03.2020; Springer Nature B.V
• Subjects: Endocrine Tumors; Medicine; Medicine & Public Health; Metastases; Metastasis; Neuroendocrine tumors; Oncology; Rectum; Risk factors; Surgery; Surgical Oncology
• ISSN: 1068-9265; 1534-4681
• DOI: 10.1245/s10434-019-07848-0

Background Small (< 2 cm) and diminutive (< 1 cm) rectal neuroendocrine tumors (RNETs) are often described as indolent lesions. A large single-center experience was reviewed to determine the incidence of metastasis and the risk factors for its occurrence. Methods Cases of RNET between 2010 and 2017 at a single institution were retrospectively reviewed. The rate of metastasis was determined, and outcomes were stratified by tumor size and grade. Uni- and multivariable predictors of metastasis were identified, and a classification and regression tree analysis was used to stratify the risk for distant metastasis. Results The study identified 98 patients with RNET. The median follow-up period was 28 months. Of the 98 patients, 79 had primary tumors smaller than 1 cm, 8 had tumors 1 to 2 cm in size, and 11 had tumors 2 cm in size or larger. In terms of grade, 86 patients had grade 1 (G1) tumors, 8 patients had grade 2 (G2) tumors, and 4 patients had grade 3 (G3) tumors. Twelve patients developed metastatic disease. Both size and grade were associated with distant metastasis in the uni- and multivariable analyses, but when stratified by grade, size was predictive of metastasis only for G1 tumors ( p  < 0.001). Among the 12 patients with metastatic disease, 3 (25%) had diminutive primary tumors, and 9 (75%) had primary tumors 2 cm in size or larger. Diminutive tumors that metastasized were all G2. Conclusions Patients with diminutive and small RNETs are at risk for metastatic disease. Tumor grade is a dominant predictor of dissemination. More rigorous staging, closer surveillance, or more aggressive initial management may be warranted for patients with G2 tumors, irrespective of size.