Assessment of pulmonary melanoma metastases with 18F-FDG PET/CT: which PET-negative patients require additional tests for definitive staging?
OBJECTIVE
To determine, in patients with melanoma, the dependence of PET sensitivity on pulmonary metastasis size, and to determine patients who require further evaluation for definite staging.


METHODS
Of 183 melanoma patients who underwent (18)F-fluorodeoxyglucose PET/computed tomography (CT) for staging or follow-up between January 2008 and June 2011, 38 patients (18 women and 20 men; mean age 62.0 ± 14.7 years) with one or more pulmonary metastases visible on CT were included in the retrospective study. Each pulmonary metastasis was rated as positive or negative on PET, and lesion size (maximum transverse diameter) was assessed on CT. PET sensitivity was calculated according to the lesions' size, in 2-mm steps.


RESULTS
A total of 181 pulmonary metastases were analysed. PET sensitivity was 7.9 % for lesions of 4-5 mm; 33.3 % for lesions of 6-7 mm; 56.8 % for lesions of 8-9 mm; 63.6 % for lesions of 10-11 mm; 100 % for lesions of 12-14 mm; and 100 % for lesions of at least 15 mm. The differences in sensitivity between the size groups were significant (P < 0.001)                                CONCLUSIONS:                  With current state-of-the-art PET/CT technology, additional tests are necessary for definitive staging of melanoma patients who have one or more PET-negative lung nodules less than 12 mm in diameter on expiratory CT.


CONCLUSIONS
• PET cannot rule out malignancy in pulmonary nodules less than 12 mm on expiratory CT.                 • Melanoma patients with PET-negative pulmonary nodules less than 12 mm require additional tests.                 • Knowledge of these factors can help interpretation of PET and PET/CT findings.
Department of Radiology, PET/CT Center, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria. marius.mayerhoefer@meduniwien.ac.at
Marius E
ME
Mayerhoefer
Helmut
H
Prosch
Christian J
CJ
Herold
Michael
M
Weber
Georgios
G
Karanikas
D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D008297:Male; D008495:Medical Oncology / Q000379:methods; D008545:Melanoma / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019788:Fluorodeoxyglucose F18