Background: Among the five subtypes of somatostatin receptor (SSTR1–5), the anti-proliferative effects of somatostatin analogs have been linked to their affinity for SSTR2. Thus, SSTR2 can be used as both a diagnostic and a therapeutic target in patients with gastroenteropancreatic neuroendocrine tumor (GEP-NET).
Methods: We evaluated SSTR2 expression by immunohistochemistry (IHC) using tumor samples of 20 GEP-NET patients receiving somatostatin analogs and it’s impact on the tumor response to somatostatin analogs and patient survival.
Results: Primary sites included 15 foregut-derived GEP-NETs [stomach (n = 3), duodenum (n = 4), biliary tract (n = 3), and pancreas (n = 5)] and 5 hindgut-derived GEP-NETs of the distal colon and rectum. Among the 20 patients, 13 (85.5%) exhibited expression of SSTR2 in tumor tissues. Expression of SSTR2 was significantly associated with low-grade WHO classification (p = 0.007), but not with gender, primary site, or number of metastatic sites. Disease control rate was superior in patients with SSTR2 positivity compared to patients with SSTR2 negativity. Moreover, the status of SSTR2 expression could significantly predict longer PFS (positive, not reached vs. negative, 2.1 months; p = 0.001).
Conclusion: SSTR2 expression had both predictive and prognostic value for survival of patients with metastatic GEP-NET receiving somatostatin analogs.