Neuroendocrine Tumors of the Large Bowel

Abstract

Summary:

Neuroendocrinetumors (NET) of the proximal part of the large intestine, i.e. cecum, ascending colon and proximal part of transversal colon, are mostly biologically inactive, so they do not cause carcinoid syndrome. Their malignant potential is slightly higher compared to rectal NETs, and metastases occur in one-third of cases at the time of diagnosis. The factors determining me-tastatic behavior include: tumor size greater than 2 cm, higher tumor grading, invasion into muscularis propria, angioinvasion and perineural invasion, metastases into lymphatic vessels and lymph nodes and higher proliferation index Ki-67. Diagnostic tactics are based on usual localization techniques, tumor staging includes performing an octreoscan as well. Prostatic acid phosphatase and serum chromogranin A are used as oncomarkers. Surgical removal is the only radical treatment. As concerns palliative therapy, there is no consensus in terms of somatostatin analogs treatment because of the absence of carcinoid syndrome in NETs in this location. Some new clinical studies confirm a tumoristatic effect even in biologically inactive NETs. Response rate is low in interferon alpha for monotherapy and for chemotherapy. Invasive forms of cytoreduction and prospectively new modalities such as targeted radiotherapy come into question. 5-year survival rate is 40-70 %.