Objective: Somatostatin receptor scintigraphy (SRS) of neuroendocrine (NE) tumours is often challenging because of minute lesion size and poor anatomic delineation. This study evaluates the impact of sequentially performed single-photon emission computed tomography (SPECT)/CT fusion on SRS study interpretation and clinical management of these tumours.
Patients and design: Seventy-two patients were studied with routine SRS and SPECT/CT at 4, 24 and optionally 48 h after injection of 222 MBq 111In-pentetreotide. Forty-five patients were evaluated for carcinoid, 15 for islet cell tumour, seven for metastatic NE tumour, four for medullary thyroid carcinoma, and one patient had ophthalmopathy. SPECT/CT induced improvement in the interpretation of SPECT and conventional CT and resultant clinical management changes were recorded.
Results: SRS was negative in 28 patients and positive in 44 patients. SPECT/CT provided no additional information in 48 patients, including all 28 negative studies. SPECT/CT improved localization of the SPECT-detected lesions in 23 of the 44 positive studies. It defined the extent of disease in 17, showed unsuspected bone involvement in three, and differentiated physiological from tumour uptake in three studies. SPECT/CT affected the clinical management in 10 patients, altered the surgical approach in six, spared unnecessary surgery in two, and modified the therapeutic modality in two patients.
Conclusions: SPECT/CT affected the diagnostic interpretation of SRS in 32% of the patients and induced changes in management in 14% of the patients.