Gut Liver.  2022 Mar;16(2):228-235. 10.5009/gnl20364.

Risk Factors for Lymph Node Metastasis and Oncologic Outcomes in Small Rectal Neuroendocrine Tumors with Lymphovascular Invasion

Affiliations
  • 1Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
  • 2Center for Colorectal Cancer, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
  • 3Department of Pathology, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
  • 4Precision Medicine, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
  • 5Department of Internal Medicine, National Health Insurance Service Ilsan Hospital, Goyang, Korea.
  • 6Divison of Gastroenterology, Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.

Abstract

Background/Aims
Small rectal neuroendocrine tumors (NETs) are often managed with local resection (endoscopic or transanal excision) owing to their low risk of metastasis and recurrence. However, the clinical significance of lymphovascular invasion in resected specimens remains controversial. In this study, we aimed to analyze the frequency of and risk factors for lymph node metastasis proven by histopathologic examination after radical resection.
Methods
We retrospectively reviewed the records of 750 patients diagnosed with a rectal NET at four academic medical centers in South Korea between 2001 and 2019. The frequency of histopathologically proven lymph node metastasis and the associated risk factors were analyzed for small tumors (≤1.5 cm) with lymphovascular invasion.
Results
Among 750 patients, 75 had a small tumor (≤1.5 cm) with lymphovascular invasion, of whom 31 patients underwent endoscopic resection only and 44 patients underwent additional radical surgery. Among the 41 patients who underwent surgery and had available data, the rate of regional lymph node metastasis was 48.8% (20/41). In multivariate analysis, the Ki-67 index (odds ratio, 6.279; 95% confidence interval, 1.212 to 32.528; p=0.029) was an independent risk factor for lymph node metastasis. During the mean follow-up period of 37.7 months, only one case of recurrence was detected in the surgery group. The overall survival was not significantly different between radical resection and local resection (p=0.332).
Conclusions
Rectal NETs with lymphovascular invasion showed a significantly high rate of regional lymph node metastasis despite their small size (≤1.5 cm).

Keyword

Rectum; Neuroendocrine tumors; Lymphovascular invasion; Metastasis
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