J Nucl Med 2000 Sep;41(9):1491-4
Which kinds of lymph node metastases can FDG PET detect? A clinical study in
melanoma.
Crippa F, Leutner M, Belli F, Gallino F, Greco M, Pilotti S, Cascinelli N,
Bombardieri E.
The purposes of this study were to establish the diagnostic accuracy of FDG PET
for lymph node metastases and to determine the smallest detectable volume of
disease. METHODS: Using FDG PET, we preoperatively studied 56 lymph node basins
in 38 patients with a clinical or instrumental diagnosis of lymph node
metastases from melanoma. All lymph node basins underwent node dissection. The
FDG PET results were compared with the postoperative histopathology results. PET
images were obtained using a GE 4096 WB scanner, after injection of a mean
activity of 496 MBq (range, 366-699 MBq) of FDG. RESULTS: The efficacy of FDG
PET in the diagnosis of involved lymph node basins was good. Sensitivity was 95%
(35/37); specificity, 84% (16/19); accuracy, 91% (51/56); positive predictive
value, 92% (35/38); and negative predicative value, 89% (16/18). Metastases were
shown histologically in 114 of 647 surgically removed lymph nodes. FDG PET
detected 100% of metastases > or = 10 mm, 83% of metastases 6-10 mm, and 23%
of metastases < or = 5 mm. Moreover, FDG PET had high sensitivity (> or =
93%) only for metastases with more than 50% lymph node involvement or with
capsular infiltration. CONCLUSION: Our study shows that FDG PET has a reasonable
sensitivity and specificity for detecting the presence or absence of lymph node
metastases in patients with melanoma. However, even if able to detect small
volumes of subclinical macroscopic disease, FDG PET cannot detect subclinical
microscopic disease with acceptable sensitivity. The specificity of FDG PET is
good, but some false-positive results may occur.
