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Role of 99mTc-HYNIC-Tyr3-octreotide scintigraphy in neuroendocrine tumors based on localization of the primary tumor.

BACKGROUND
The aim of our work was to determine the accuracy of 99mTc-HYNIC Tyr3 octreotide scintigraphy (TcOS) in detecting active disease in neuroendocrine tumors (NETs) based on embryological origin of the primary tumor (foregut, midgut or hindgut).


METHODS
We analyzed retrospectively 45 studies (12 staging, 26 suspicion of recurrence, and 7 treatment response) belonging to 33 patients with histological confirmation of NETs. Whole body scan and a SPECT-CT were acquired 4 hours post-injection of 740 MBq of 99mTc-HYNIC Tyr3 octreotide. The studies were divided into 3 groups based on the embryological origin of primary tumor (foregut [group 1], midgut [group 2] and hindgut [group 3]). The accuracy of TcOS in each group was assessed, included chi-square analyses. The final diagnosis was established by histopathology or clinical/radiological follow-up greater than 6 months.


RESULTS
The localization of the primary tumor per patient revealed that 58% were from the foregut, 30% from the midgut and 12% from the hindgut. In study-based analysis (45 studies), TcOS showed an overall sensitivity, specificity and accuracy of 95%, 92% and 93% respectively. The accuracy per studies for the groups 1, 2 and 3 were: 100%, 92% and 66% respectively, demonstrating a better detection of active disease in primary tumors from foregut and midgut compared to hindgut (P=0.02).


CONCLUSIONS
The accuracy of TcOS in the assessment of NETs seems to be better in tumors with foregut and midgut origin, showing a possible relationship between the embryological origin of NETs and detection of active disease by TcOS.