In vivo detection of malignant thymic masses by indium-111-DTPA-D-Phe1-octreotide scintigraphy.
Many tumors with neuroendocrine characteristics express high amounts of somatostatin receptors that enable in vivo imaging with [(111)In-DTPA-D-Phe1]-octreotide. In this study, we have analyzed the feasibility in detecting and characterizing thymic masses by somatostatin receptor scintigraphy (SRS).


METHODS
Eighteen patients (13 women, 5 men, ages 18-78 yr; mean +/- s.d. = 42.1 +/- 17.6 yr) were enrolled in this study. Eleven patients were studied during diagnosis and seven during routine follow-up. In seven patients, myasthenia gravis was the presenting symptom. SRS was performed within 4 wk after CT and/or MRI. Planar and tomographic images were acquired within 24 hr after the injection of approximately 111 MBq of [(111)In-DTPA-D-Phe1]-octreotide. The scintigraphic results were categorized according to the histologic findings.


RESULTS
Histology diagnosed 10 mixed epithelial/lymphoid thymomas (8 with prevalent epithelial component), 2 thymic carcinomas, 1 thymic carcinoid, 1 lymphangioma and 4 thymic hyperplasias. Two thymoma were Stage I, 3 were Stage II, 2 were Stage III and 5 were Stage IV, as was the thymic carcinoid. Indium-111-DTPA-D-Phe1-octreotide concentrated in primary and/or metastatic sites of thymic tumors, thereby enabling successful external gamma imaging of sites greater than 1.5 cm in size. Tumor-to-lung (T/L) ratios were as high as 7.6-fold (range 1.7-7.6). Untreated thymomas showed higher T/L (4.34 +/- 1.57) than treated ones (2.68 +/- 1.18). No uptake was detectable in the four patients with benign thymic hyperplasia and the patient with the lymphangioma.


CONCLUSIONS
Indium-111-DTPA-D-Phe1-octreotide is avidly concentrated within thymic tumors, but it is not concentrated by thymic hyperplasia, which allows differential diagnosis. Thus, in patients with myasthenia gravis, SRS may have a role in characterizing thymic masses, thereby overcoming the limits of cross-sectional imaging modalities.
Lastoria
S
S
Department of Nuclear Medicine National Cancer Institute, Fondazione G. Pascale, Naples, Italy.
Vergara
E
E
Palmieri
G
G
Acampa
W
W
Varrella
P
P
Caracò
C
C
Bianco
R A
RA
Muto
P
P
Salvatore
M
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D002276:Carcinoid Tumor / Q000000981:diagnostic imaging; D002277:Carcinoma / Q000000981:diagnostic imaging; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000031:analogs & derivatives*; D004369:Pentetic Acid / Q000031:analogs & derivatives*; D019275:Radiopharmaceuticals; D013945:Thymoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D013952:Thymus Hyperplasia / Q000175:diagnosis / Q000000981:diagnostic imaging; D013953:Thymus Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; C071632:SDZ 215-811; D004369:Pentetic Acid; D015282:Octreotide