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

Purpose Our aim was to assess the prognostic and predictive value of somatostatin receptor 2 (sstr2) in neuroendocrine tumors (NETs). Methods We established a tissue microarray and imaging database from NET patients that received sstr2-targeted radiopeptide therapy with yttrium-90-DOTATOC, lutetium177- DOTATOC or alternative treatment. We used univariate and multivariate analyses to identify prognostic and predictive markers for overall survival, including sstr2-imaging and sstr2immunohistochemistry. Results 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). Conclusions 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.