The prognostic and predictive value of sstr₂-immunohistochemistry and sstr₂-targeted imaging in neuroendocrine tumors.

Abstract

Our aim was to assess the prognostic and predictive value of somatostatin receptor 2 (sstr₂) in neuroendocrine tumors (NETs). We established a tissue microarray and imaging database from NET patients that received sstr₂-targeted radiopeptide therapy with yttrium-90-DOTATOC, lutetium-177-DOTATOC or alternative treatment. We used univariate and multivariate analyses to identify prognostic and predictive markers for overall survival, including sstr₂-imaging and sstr₂-immunohistochemistry. We included a total of 279 patients. In these patients, sstr₂-immunohistochemistry was an independent prognostic marker for overall survival (HR: 0.82, 95 % CI: 0.67 - 0.99, n = 279, p = 0.037). In DOTATOC patients, sstr₂-expression on immunohistochemistry correlated with tumor uptake on sstr₂-imaging (n = 170, p < 0.001); however, sstr₂-imaging showed a higher prognostic accuracy (positive predictive value: +27 %, 95 % CI: 3 - 56 %, p = 0.025). Sstr₂-expression did not predict a benefit of DOTATOC over alternative treatment (p = 0.93). Our results suggest sstr₂ as an independent prognostic marker in NETs. Sstr₂-immunohistochemistry correlates with sstr₂-imaging; however, sstr₂-imaging is more accurate for determining the individual prognosis.