title: Influence of PET/CT 68Ga somatostatin receptor imaging on proceeding with patients, who were previously diagnosed with 99mTc-EDDA/HYNIC-TOC SPECT.
abstract: BACKGROUND
  The aim of this study was the assessment of utility of somatostatin receptor scintigraphy (SRS) by SPECT imaging using 99mTc-EDDA/HYNIC-Tyr3-octreotide (99mTc-EDDA/HYNIC-TOC) in patients with neuroendocrine neoplasm (NEN) or suspected NEN, referred to Nuclear Medicine Dept. of Voivodship Specialty Center in Rzeszow. The selected group of patients was referred also to 68Ga PET/CT. The posed question was the ratio of patients for whom PET/CT with 68Ga would change their management.
  
  
  METHODS
  The distribution of somatostatin receptors was imaged using 99mTc-EDDA/HYNIC-TOC in 61 planar and SPECT studies between 13/05/2010 and 04/02/2013 in Nuclear Medicine Dept. of Voivodship Specialty Center in Rzeszow. The patient age was within a range of 17-80, with the average age of 57.6. The average age of women (65% of patients over-all) was 55.6 and the average age of men (35% of patients overall) was 61.4. In 46 participants (75% of the study group), that underwent SRS, NEN was documented using pathology tests. Selected patients were referred to PET/CT with 68Ga labeled somatostatin analogs, DOTATATE or DOTANOC. This study group consisted of 14 female and 10 male participants with age range of 35-77 and average age of 55.5 years. Patients were classified into 3 groups, as follows: detection - referral due to clinical symptoms and/or biochemical markers (CgA-Chromogranin A, IAA-indoleacetic acid) with the aim of primary diagnosis, staging - referral with the aim of assessment of tumor spread, and follow-up - assessment of the therapy.
  
  
  RESULTS
  Out of 61 patients, 24 underwent both 99mTc-EDDA/HYNIC-Tyr3-octreotide SPECT and 68Ga PET/CT. The result of PET/CT was used as a basis for further evaluation. Therefore, the patients were divided into groups; true positive TP (confirmed presence of tissue somatostatin receptors with 68Ga PET/CT) and TN (68Ga PET/CT did not detect any changes and the results were comparable and had the same influence on treatment protocol). In case of SPECT, the results were assigned as follows: TP, TN (in cases where the results were confirmed by 68Ga PET/CT), FP (patient's scintigraphy demonstrated focal change by SPECT but not PET/CT) and FN (99mTc-EDDA/HYNIC-Tyr3-octreotide SPECT failed to demonstrate any abnormalities; however, the treatment protocol was changed after PET/CT).
  
  
  CONCLUSIONS
  The accuracy of SPECT diagnosis was found to be as high as 91.6%. Only in 8.4% of patients the additional PET/CT with 68Ga-labeled somatostatin analog changed the treatment protocol.
authors.affiliation: Department of Nuclear Medicine, Voivodship Medical Specialty Center, Rzeszow, Poland. dmadrzak@gmail.com.
authors.forename: Dorota
authors.initials: D
authors.lastname: Madrzak
authors.forename: Renata
authors.initials: R
authors.lastname: Mikołajczak
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Kamiński
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging / Q000378:metabolism; D015282:Octreotide / Q000031:analogs & derivatives* / Q000737:chemistry; D015609:Organotechnetium Compounds / Q000737:chemistry*; D000072078:Positron Emission Tomography Computed Tomography; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult
chemical_list: D005710:Gallium Radioisotopes; D015609:Organotechnetium Compounds; D017481:Receptors, Somatostatin; C410263:technetium Tc 99m hydrazinonicotinyl-Tyr(3)-octreotide; C026058:EDDA; D004492:Edetic Acid; D015282:Octreotide
keywords: 68Ga; 99mTc-EDDA/HYNIC-Tyr3-octreotide; PET; SPECT; SRS; somatostatin receptor imaging