The Value of Somatostatin Receptor Scintigraphy (SRS) in Patients with NETG1/G2 Pancreatic Neuroendocrine Neoplasms (p-NENs).

BACKGROUND: Neuroendocrine neoplasms of the pancreas (p-NEN) are common gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs). The aim of this retrospective study was to review the of value of Somatostatin Receptor Scintigraphy (SRS) in initial detection of p-NEN, evaluation of tumour extent and as imaging follow-up after radical surgery in patients with confirmed well (NETG1) or moderate (NETG2) differentiated p-NEN based on pathological WHO 2017 classification.

MATERIAL AND METHODS: Overall 281 patients with confirmed p-NEN were enrolled. The SRS was performed to evaluation of primary p-NEN, also to assess clinical stage of disease, based on current World Health Organization (WHO) classification and during clinical follow-up. A total of 829 examinations were performed over time in these 281 patients using 99mTc HYNICTOC. Images were acquired between 1 - 3 h after i.v. injection of radiotracer. Initially whole body WB-SPECT and then WB-SPECT/CT, with standard iterative reconstruction were used.

RESULTS: There were 159 patients with NETG1 (57%) and 122 subjects with NETG2 (43%). The female to male ratio was 1.1:1. In 68 patients (22%) with NETG1/G2 eight-seven SRS (10%) were performed to confirm initial diagnosis. SRS results were as follow: true positive (TP) = 84 (97%), false negative (FN) = 3 (3%), no true negative (TN) or false positive (FP) results of SRS examination (sensitivity of SRS per patient was 96%). In 198 subjects (66%) SRS was used in evaluation and re-evaluation of the clinical stage, A total of 661 (80%) examinations were carried out in these patients. There were TP=514 (77%), TN=136 (21%), FN=7 (1%) and FP=4 (1%) results. The sensitivity and specificity per patient were: 96% and 95%. The sensitivity and specificity per study: 98% and 97%. In 35 patients (12%) SRS was used as imaging follow-up after radical surgery, there were overall 81 examination (10%) which were performed. There were 76 (91%) TN results of examinations of SRS and in 4 patients we identified recurrence (TP). In total, which consists of initial diagnosis/staging and follow-up patients, the sensitivity of SRS was 96% and specificity 97% per patient and per study sensitivity and specificity was 98%.

CONCLUSIONS: SRS using 99mTc HYNICTOC acquired in WB-SPECT or WB-SPECT/CT techniques is an excellent imaging modality in detection of primary NETG1/G2 p-NEN. Our study confirms that SRS has high sensitivity and specificity, as a result has tremendous value as an examination method to assess clinical stage of disease and as an imaging follow-up after radical treatment.