The prognostic and predictive value of sstr 2 -immunohistochemistry and sstr 2 -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, 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.

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.