Comparison of 18F-DOPA, 18F-FDG and 68Ga-somatostatin analogue PET/CT in patients with recurrent medullary thyroid carcinoma.
OBJECTIVE
To retrospectively evaluate and compare (18)F-FDG, (18)F-DOPA and (68)Ga-somatostatin analogues for PET/CT in patients with residual/recurrent medullary thyroid carcinoma (MTC) suspected on the basis of elevated serum calcitonin levels.


METHODS
Included in the study were 18 patients with recurrent MTC in whom functional imaging with the three tracers was performed. The PET/CT results were compared on a per-patient basis and on a per-lesion-basis.


RESULTS
At least one focus of abnormal uptake was observed on PET/CT in 13 patients with (18)F-DOPA (72.2% sensitivity), in 6 patients with (68)Ga-somatostatin analogues (33.3%) and in 3 patients with (18)F-FDG (16.7%) (p < 0.01). There was a statistically significant difference in sensitivity between (18)F-DOPA and (18)F-FDG PET/CT (p < 0.01) and between (18)F-DOPA and (68)Ga-somatostatin analogue PET/CT (p = 0.04). Overall, 72 lesions were identified on PET/CT with the three tracers. (18)F-DOPA PET/CT detected 85% of lesions (61 of 72), (68)Ga-somatostatin analogue PET/CT 20% (14 of 72) and (18)F-FDG PET/CT 28% (20 of 72). There was a statistically significant difference in the number of lymph node, liver and bone lesions detected with the three tracers (p < 0.01). In particular, post-hoc tests showed a significant difference in the number of lymph node, liver and bone lesions detected by (18)F-DOPA PET/CT and (18)F-FDG PET/CT (p < 0.01 for all the analyses) and by (18)F-DOPA PET/CT and (68)Ga-somatostatin analogue PET/CT (p < 0.01 for all the analyses). The PET/CT results led to a change in management of eight patients (44%).


CONCLUSIONS
(18)F-DOPA PET/CT seems to be the most useful imaging method for detecting recurrent MTC lesions in patients with elevated serum calcitonin levels, performing better than (18)F-FDG and (68)Ga-somatostatin analogue PET/CT. (18)F-FDG may complement (18)F-DOPA in patients with an aggressive tumour.
Institute of Nuclear Medicine, Policlinico A. Gemelli, Catholic University of the Sacred Heart, Rome, Italy. giorgiomednuc@libero.it
Giorgio
G
Treglia
Paola
P
Castaldi
Maria Felicia
MF
Villani
Germano
G
Perotti
Chiara
C
de Waure
Angelina
A
Filice
Valentina
V
Ambrosini
Nadia
N
Cremonini
Monica
M
Santimaria
Annibale
A
Versari
Stefano
S
Fanti
Alessandro
A
Giordano
Vittoria
V
Rufini
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002116:Calcitonin / Q000097:blood; D018278:Carcinoma, Neuroendocrine; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D005260:Female; D019788:Fluorodeoxyglucose F18; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D057285:Precision Medicine; D012008:Recurrence; D012189:Retrospective Studies; D013004:Somatostatin / Q000031:analogs & derivatives*; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
D005710:Gallium Radioisotopes; D019788:Fluorodeoxyglucose F18; C043437:fluorodopa F 18; D013004:Somatostatin; D004295:Dihydroxyphenylalanine; D002116:Calcitonin