Endocrine Abstracts

Background: The expression and/or co-expression of somatostatin (sstr1–5) and dopamine (DR) receptors in neuroendocrine tumors (NETS) is of clinical interest as their expression implies that NETS could be treated with combined targeted therapy. In addition, the expression of sstrs permits tumour visualization with radiolabelled sst analogs (¹¹¹In-DTPA-OctreoScan).

Methods: We analyzed preoperative Octreoscans findings (also graded for the radioligand uptake as visual score) of 96 patients (53 males) with NETS and compared them with their immunohistochemical (IHC) reactivity for sstr2, sstr3, sstr5 in all samples and D2R in a subset of patients. The findings of both methods were compared.

Results: 70 patients had gastrointestinal (GI)-NETS and 26 lung NETS. In 67/96 cases (69.8%) there was concordance of the IHC (all sstr2 positive) with the findings of the Octreoscan (P<0.001), while in 17.8% cases positive ICH was seen along with negative Octreoscan and in 12.5% positive octreoscan was seen along with negative IHC. In 60 cases (62.5%) sstr2 was expressed and in lesser rates sstr3 and sstr5 (29.5 and 20.8% respectively). In GI-NETS, the concordance between the two methods decreased in 45/70 (64.3%) (P=0.25) while in lung NETS increased in 22/26 (84.6%) (P=0.003). Octreoscan score had a high positive correlation with sstr2 (r=0.6, P<0.001), sstr3 (r=0.4, P<0.001) and D2R (r=0.5, P=0.01) expression, while sstr2 expression was positively correlated with sstr3 (r=0.6, P<0.001) and sstr5 (r=0.5, P<0.001) and between sstr3 and sstr5 (r=0.5, P<0.001). Sstr2 expression was positively related to D2R only in small sized tumors (<2 cm) (r=0.8, P=0.001) while in large sized tumours octreoscan score was no more related to D2R expression. Tumour diameter and sstr2 IHC were the only parameters that could predict the positivity of octreoscan in the multivariate logistic analysis (P=0.001, OR: 1.061, CI: 1.024–1.098 and P=0.011, OR: 5.502, CI: 1.482–20.424 respectively).

Conclusions: Both methods, IHC expression of sstrs and Octreoscan are of great importance and they complement each other. The expression of DR2 in such tumours is of potential clinical significance.