The use of octreotide scans in the diagnosis and follow-up of neuroendocrine tumors (NETs).

Abstract

e14631 Background: NETs are usually diagnosed and followed via a variety of imaging modalities, including MRI, CT scans and somatostatin scintigraphy (OctreoScan, SRS). SRS works by detecting somatostatin receptors found on NETs. There is ongoing debate as to which imaging modality should routinely be used to diagnose and follow patients affected with NETs. This project aims to determine if the information gathered from SRS corresponds or adds to results obtained from modern CT or MRI. Methods: We conducted a retrospective chart review by identifying all patients diagnosed with a NET who were seen at TOHCC between 2003-01-01 and 2009-03-31. We then identified all patients who underwent an SRS within 30 days of a CT or MRI. Results of the SRS were then compared against those of the latter imaging modalities. Results: 70 patients with a diagnosis of NET were identified. Of these, 28 had an SRS within 30 days of a CT or MRI. 5 patients had serial SRS plus either a CT or MRI within the defined time window. In total, 33 SRS results were allowed in the study. When compared to the results of the CT or MRI, 13 (39.4%) were true negatives (TN) SRS, 9 (33.3%) were true positives (TP), and 8 (24.3%) were false negatives (FN) in the setting of metastatic disease. The liver was the most common site missed. One patient had a false positive (FP) SRS (3.0%) with the location of the supposed lesion thought to be in the small bowel. Conclusions: The sensitivity of CT scans and MRIs is superior to that of SRS when investigating NET. There were no cases were an SRS identified lesions that were truly present but not seen on CT or MRI. The most common site missed by the SRS was the liver. This data suggest that SRS does not provide additional information and does not appear to be useful in the diagnosis and follow up of patients with NET, however, further research is needed.