Low efficacy of 18F-FDG PET for detection of uveal malignant melanoma compared with 123I-IMP SPECT.
Earlier investigations showed that N-isopropyl-p-123I-iodoamphetamine SPECT (123I-IMP SPECT) is useful for the diagnosis of uveal malignant melanoma, whereas the feasibility and usefulness of 18F-FDG PET in uveal malignant melanoma have not yet been established. We compared the usefulness of 123I-IMP SPECT and 18F-FDG PET for the detection of uveal malignant melanoma on the same subjects.


METHODS
Nineteen patients (10 men, 9 women) with suspected uveal malignant melanoma were examined by 123I-IMP SPECT. Thirteen of them were also examined by 18F-FDG PET. 123I-IMP SPECT was performed at 15 min or at 3 and 24 h after intravenous administration of 123I-IMP.


RESULTS
In 12 of 19 study patients, 123I-IMP SPECT obtained at 24 h after intravenous administration of 123I-IMP delineated an area of increased uptake in the site corresponding to the ocular tumor. All of the ocular tumors in the 12 123I-IMP SPECT-positive patients were confirmed histopathologically and clinically to be uveal malignant melanoma. The other 7 123I-IMP-SPECT-negative patients have been monitored under the diagnosis of choroidal nevus, choroidal hemangioma, hyperplasia of the pigment epithelium of the retina, or idiopathic inflammatory lesions without any complications. In a total of 13 patients examined by 18F-FDG PET, 9 of whom were 123I-IMP SPECT positive and 4 were negative, only 1 patient showed abnormal uptake of 18F-FDG PET in the site corresponding to the ocular tumor. Therefore, 8 of 9 patients with uveal malignant melanoma showed false-negative results in 18F-FDG PET. The 18F-FDG PET-positive patient with uveal malignant melanoma had the largest tumor mass with a short diameter of 12 mm, a long diameter of 17 mm, and a height of 7 mm. In the other 8 18F-FDG PET-negative patients, the tumors had a dimension of 11 x 13 x 7 mm or less.


CONCLUSIONS
123I-IMP SPECT is a sensitive and accurate method for the detection of uveal malignant melanoma, whereas the efficacy of 18F-FDG PET for this purpose is low because of a high incidence of false-negative results. 123I-IMP SPECT is far more superior in comparison with 18F-FDG PET in detecting uveal malignant melanoma.
Kato
Katsuhiko
K
Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan. katokt@med.nagoya-u.ac.jp
Kubota
Toshinobu
T
Ikeda
Mitsuru
M
Tadokoro
Masanori
M
Abe
Shinji
S
Nakano
Satoshi
S
Nishino
Masanari
M
Kobayashi
Hidetoshi
H
Ishigaki
Takeo
T
D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D020367:Iofetamine; D008297:Male; D008545:Melanoma / Q000000981:diagnostic imaging*; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014604:Uveal Neoplasms / Q000000981:diagnostic imaging*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D020367:Iofetamine