Imaging of soft-tissue tumors using L-3-[iodine-123]iodo-alpha-methyl-tyrosine single photon emission computed tomography: comparison with proliferative and mitotic activity, cellularity, and vascularity.
The radiolabeled amino acid L-3-[123I]-iodo-alpha-methyltyrosine (IMT) is a new tumor tracer that accumulates in many tumors and is suitable for single photon emission computed tomography (SPECT) imaging. Using IMT SPECT, we studied 32 patients with a soft-tissue tumor suspected to be a soft-tissue sarcoma to determine whether: (a) tumors can be visualized; (b) benign and malignant lesions can be distinguished; and (c) IMT uptake is related to tumor grade and proliferation. Whole-body imaging was performed 15 min after administration of 300 MBq IMT, biopsy, or resection 1-2 weeks later. IMT uptake was quantified using a region-of-interest method resulting in tumor:background (T:B) ratios. These were compared with tumor grade, mitotic index, tumor cellularity, vascularity, and the Ki-67 proliferation index. Eleven patients had a benign tumor, and 21 patients had a soft-tissue sarcoma. Six benign tumors demonstrated minor IMT uptake, and five lipomas had no uptake. All malignant tumors had high uptake and were clearly visualized. T:B ratios in malignant tumors (3.83 +/- 1.16) were higher (P < 0.001) than in benign tumors (1.52 +/- 0.60). Small (<5 mm) metastases in two patients were not detected. Taking the T:B ratio 2.0 as the cutoff level, the sensitivity for detection of malignancy was 100%, and specificity was 88%. IMT uptake correlated with histological grade (r = 0.82; P < 0.001), mitotic index (r = 0.75; P < 0.001), tumor cellularity (r = 0.73; P < 0.01), and with the Ki-67 proliferation index (r = 0.63; P < 0.01). In conclusion, IMT SPECT visualized all soft-tissue sarcomas. Uptake in sarcomas was clearly higher than in benign lesions, yielding 100% sensitivity for detection of malignancy at 88% specificity. Uptake increased with higher tumor grade and higher proliferation rate.
Jager
P L
PL
Department of Nuclear Medicine, University Hospital Groningen, The Netherlands. p.l.jager@nucl.azg.nl
Plaat
B E
BE
de Vries
E G
EG
Molenaar
W M
WM
Vaalburg
W
W
Piers
D A
DA
Hoekstra
H J
HJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002455:Cell Division; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000096:biosynthesis; D008297:Male; D008781:Methyltyrosines; D008875:Middle Aged; D008938:Mitosis; D009362:Neoplasm Metastasis; D009389:Neovascularization, Pathologic; D012509:Sarcoma / Q000098:blood supply / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000098:blood supply / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology*; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods*; D015899:Tomography, Emission-Computed, Single-Photon
D019394:Ki-67 Antigen; D008781:Methyltyrosines; C030855:3-iodo-alpha-methyltyrosine