The pattern of SSTRs expression in neuroendocrine neoplasms determines the possibility of the detection of the primary tumour and distant metastases, the application of radio-guided surgery (RGS) and the outcome of the treatment with itrium or lutetium labeled somatostatin analogues. The frequency and expression pattern of each subtype of SSTRs not only vary considerably in different NET but also in each patient.
The aim of the study was to assess the SSTR expression pattern in GEP-NET and MTC patients.
Material and methods: The study included 32 patients diagnosed with GEP-NET (14 with gastrointestinal, 8 with pancreatic and 2 with bronchial NETs) or MTC (8 patients). (99mTc-EDDA/HYNIC)octreotate (somatostatin analogue with high affinity to SSTR2) scintigraphy (SRS) was performed in all patients before surgery. SSTR1-SSTR5 expression was assessed immunohistochemically in paraffin embedded tumour tissues with use of polyclonal antibodies (Gramsch-Schwabhausen, Germany). Expression intensity was assessed in 03 semi-quantitative scale.
Results: The SSTR1 was detected in 56.3%, SSTR2 in 87.5%, SSTR3 in 31.3% and SSTR5 in 53.1% of samples. No tumour showed the expression of SSTR4. No SSTRs expression was found in five patients (four GEP-NETs, one MTC).
Preoperative SRS was negative in 6 patients, which correlated with no or very weak expression of SSTRs. The target/non-target ratio (SRS) did not correspond with SSTRs expression intensity. Surprisingly, in some patients with relatively low expression of SSTR2 high quality SRS was obtained. In 5 patient with positive SRS, RGS was performed, which enabled localization of preoperatively occult primary or metastatic lesions all of them showed expression of SSTR2 in tumour tissues. Eight patient of the study group underwent palliative 90Y-DOTATATE therapy.
Conclusions: No SSTRs expression results in false-negative SRS. Even weak positivity for SSTRs may enable detection of the occult primary and metastatic NET lesions with RGS and further treatment with hot somatostatin analogues.
03 - 07 May 2008
European Society of Endocrinology