Prognostic value of somatostatin receptor-2 positivitiy in gastroenteropancreatic neuroendocrine tumors in reference to known prognostic factors.

Background/aims: Identification of the predictive factors for the prognosis of gastroenteropancreatic neuroendocrine tumors is important but rather challenging due to the rarity of the condition. This study aimed to examine the association between somatostatin receptor-2 positivity and known prognostic factors for gastroenteropancreatic neuroendocrine tumor to identify the value of somatostatin receptor-2 positivity itself as a predictive factor for prognosis.

Materials And Methods: Records of 41 gastroenteropancreatic neuroendocrine tumor patients (24 females, 17 males) were retrospectively reviewed. The relations between somatostatin receptor-2 positivity and known prognostic factors including tumor stage, Ki-67 positivity, vascular or perineural invasion, lymph node metastasis, presence of necrosis, and soft tissue extension were analyzed.

Results: Sixty percent of the patients had histologically confirmed somatostatin receptor-2 positivity with 45% exhibiting focal and 15% showing diffuse staining characteristic. No significant relation was found between somatostatin receptor-2 positivity and any of the known prognostic factors for gastroenteropancreatic neuroendocrine tumor: versus stage, p=0.67; vs. lymph node metastasis, p=0.51; vs. vascular invasion, p=0.11; vs. extension to surrounding soft tissue, p=0.54; vs. necrosis, p=0.23; vs. lymphatic invasion, p=0.25; and vs. perineural invasion, p=0.42.

Conclusions: Somatostatin receptor-2 positivity, either focal or diffuse, does not seem to predict prognosis in gastroenteropancreatic neuroendocrine tumors. However, growing evidence supports the benefits of somatostatin analogues as adjunctive treatment in this group of patients.