Prognostic marker of immunohistochemistry-based somatostatin receptors 2 and 5 H-scores in patients with pancreatic neuroendocrine neoplasms

Pancreatic neuroendocrine neoplasms (pNENs) are histologically classified as well-differentiated, poorly-differentiated, or mixed neuroendocrine-non-neuroendocrine neoplasms. There are unresectable pNENs owing to metastases or invasion in not only functional pNENs but also non-functional. However, the exact origin of pNENs has not been elucidated. This study aims to characterize the molecular biology of pNENs based on clinical information and histopathological analysis and identify prognostic biomarkers. We investigated the relationship between the biological characteristics and immunostaining of pathological tissues in 75 patients. Staining density was evaluated on a 4-point scale from 0 to 3, and the percentage of tumor cells was calculated and scored from 0 to 300 (H-score). We performed receiver operating characteristic (ROC) curve analysis of the H-score. Progression-free survival and overall survival analyses were performed based on the Kaplan–Meier curves. The H-score showed that patients who died of pNEN had high Ki-67 and low somatostatin receptor (SSTR) 2 levels, and those who relapsed had high Ki-67 and low SSTR5 levels. The ROC showed that the SSTR2 H-score > 80.25 was associated with lower mortality, which was further confirmed by Kaplan–Meier curves [hazard ratio (HR): 6.039, 95 % confidence interval (CI): 1.233–29.59, P = 0.0006). SSTR5 H-score > 93.9 had less recurrence, which was confirmed using Kaplan–Meier curves (HR: 3.321, 95 % CI: 1.426–7.734, P = 0.0336). Ki-67 > 4.95 is associated with a significantly increased risk of death. Quantification of SSTR2 and SSTR5 immunostaining using the H-score may serve as prognostic markers.