Updating the management of patients with rectal neuroendocrine tumors

Abstract

Rectal neuroendocrine tumors (NETs) account for approximately one-third of all digestive NETs, with an increasing incidence and good overall prognosis. Although recent guidelines have been published, endoscopic techniques have expanded substantially and the most recent reports should be taken into account for clinical practice. The objectives of this report were to review the latest advances on prognosis, pre-interventional explorations, treatment-with particular focus on endoscopy-and surveillance of well-differentiated rectal NETs, excluding poorly differentiated and metastatic tumors.

Excellent prognosis following endoscopic resection of patients with rectal neuroendocrine tumors despite the frequent presence of lymphovascular invasion

“…Currently, several different techniques are available for ER of rectal NETs [23][24][25][26][27][28][38][39][40][41]. We have reported an excellent R0 resection rate of ESMR-L as compared with the rate obtained with polypectomy and conventional EMR [39,40].…”

Is endoscopic ultrasonography essential for endoscopic resection of small rectal neuroendocrine tumors?

“…Risk factors for metastasis include tumor size, muscularis propria invasion, histologic grade (Ki-67 index and mitotic count), lymphovascular invasion, neural invasion, and atypical endoscopic features[10,16]. In particular, presence of a > 10-mm tumor size and lymphatic invasion strongly corresponded to LN metastasis, with the rate of LN metastasis increasing to 16% with either one of these two risk factors, and further increased to as high as 77% in patients with both risk factors[17].…”

Frequent Presence of Lymphovascular Invasion in Small Rectal Neuroendocrine Tumors on Immunohistochemical Analysis

“…The complete resection rate pooled from 14 studies has been found to be 59.1% with polypectomy or EMR for RNETs (range 17-90%) [10]. To achieve clear resection margins, more advanced techniques such as endoscopic submucosal dissection (ESD), endoscopic submucosal resection with a ligation device (ESMR-L; fig.…”

“…Therefore, recent guidelines recommend additional treatment for RNETs if LVI is presented after ER [10,17]. Previous studies have shown that small RNETs have a very low incidence of LVI [18,19,20,21].…”

“…The updated European Neuroendocrine Tumor Society consensus guideline and the Japanese Neuroendocrine Tumor Society guideline recommend additional radical surgery combined with lymph node dissection even for RNETs ≤10 mm if LVI is detected [10,17]. In accordance with these guidelines, nearly 50% of patients examined using immunohistochemical analysis would require additional radical surgery because of the presence of LVI following ER.…”