Satoshi Kato, Presenter: Nothing to Disclose

Atsushi Nambu MD, Abstract Co-Author: Nothing to Disclose

Akitoshi Saito, Abstract Co-Author: Nothing to Disclose

Keiko Matsumoto MD, Abstract Co-Author: Nothing to Disclose

Keiichi Ishigame MD, PhD, Abstract Co-Author: Nothing to Disclose

Tsutomu Araki MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to evaluate the usefulness of delayed scan of 18fluorine fluorodeoxyglucose positron emission tomography (18F-FDG PET) for the diagnosis of lymph node metastasis in non-small cell lung cancer (NSCLC).

The subjects were 82 patients with NSCLC (52 adenocarcinomas, 24 squamous cell carcinomas, 6 other lung carcinomas),  who were underwent surgical nodal staging. A total of 462 lymph node stations (242 mediastinal lymph node stations and 220 hilar lymph node stations) were evaluated histologically for the presence or absence of metastasis. All patients received PET scan at 60 min (early scan) and 120 min (delayed scan) after injection of 18F-FDG. The maximum standardized uptake values (SUV) of their lymph node stations were measured at early and delayed phase. For the lymph node stations that showed clear accumulation (defined as SUV of 1.5 or more at early phase), we calculated the retention index (RI=[delayed SUV - early SUV] / early SUV X 100%). In addition, we evaluated the diagnostic ability of lymph node metastasis when using the combined criteria of early SUV and RI in comparison with that of early SUV alone.

Fifty-four lymph node stations (18 mediastinal lymph node stations and 36 hilar lymph node stations) had proven metastases histologically. The mean RIs of the lymph node stations were as follows; 18.36% for mediastinal lymph node stations with metastasis, -1.96% without metastasis; 16.93% for hilar lymph node stations with metastasis; -0.50% without metastasis. There was a statistically significant difference (p<0.05) in mean RI between the lymph node stations with and without metastasis of each location. When the cut-off value of SUV at early scan as the criterion of malignancy was set at 2.5 or 2.0, the sensitivities, specificities, and accuracies were 39.6%, 92.9% and 87.2% (SUV>2.5), 61.1%, 79.4% and 77.3% (SUV>2.0), respectively. If RI more than 10% was added into the criterion, the sensitivities, specificities, and accuracies became 34.0%, 97.8% and 90.5% (SUV>2.5), 53.7%, 95.6% and 90.7% (SUV>2.0), respectively.

Metastatic lymph nodes have a higher RI than non-metastatic ones. The combined criteria of early SUV and RI can improve the accuracy of the diagnosis of lymph node metastasis in NSCLC.

Addition of delayed scan can improve accuracy of the diagnosis of the lymph node metastasis in NSCLC

Kato, S, Nambu, A, Saito, A, Matsumoto, K, Ishigame, K, Araki, T, Usefulness of Delayed Scan of 18F-FDG PET for the Diagnosis of Lymph Node Metastasis in Non-Small Cell Lung Cancer.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6009251.html