NEW ORLEANSThe high negative predictive value of positron
emission tomography (PET) imaging can spare some patients with early
non-small-cell lung cancer (NSCLC) the need for mediastinoscopy prior
Michael P. Farrell, MD, said at the American Roentgen Ray Society
annual meeting. Dr. Farrell and his colleagues from the Department of
Radiology, Duke University Medical Center, have demonstrated that
fluorodeoxyglucose (FDG)-PET imaging can detect micrometastases that
computed tomography (CT) may miss.
Disease stage at presentation dictates the management of NSCLC.
Although stage I-IIIa NSCLC is considered to be potentially operable,
about 20% to 30% of patients with no evidence of lymph node
involvement or widespread metastases on CT nonetheless have
mediastinal lymph node metastases. CT is suboptimal because it can
fail to detect micrometastases in normal-sized nodes.
At many institutions, stage I patients are referred for
mediastinoscopy prior to thoracotomy. Mediastinoscopy,
Dr. Farrell noted, is stressful and requires general
anesthesia. In addition, sampling techniques are variable.
Since the sensitivity of CT is only 60% for identifying nodal
metastases, Dr. Farrell and his colleagues asked whether FDG-PET
imaging, a noninvasive method, could distinguish those patients who
require nodal sampling from those who should go immediately to
FDG-PET images from 96 patients were retrospectively reviewed: 70 had
nodal sampling at thoracotomy, and 20 had undergone mediastinoscopy.
The remaining 6 patients were referred for radiotherapy due to poor
respiratory function and were excluded from the study.
The FDG-PET technique correctly staged 82% of the cases, overstaged
12%, and understaged 5%. The sensitivity of FDG-PET was 0.56 for
detecting involved hilar lymph nodes, and the specificity was 0.95.
Although the sensitivity for hilar nodes is relatively low, he said,
this doesnt alter management because these patients go directly
to thoracotomy regardless.
For mediastinal nodes, FDG-PET had a sensitivity of 0.8 and a
specificity of 0.92, with a positive predictive value of 0.36 and a
negative predictive value of 0.99. With such a high negative
predictive value, stage I NSCLC patients with a negative FDG-PET scan
can proceed directly to thoracotomy, Dr. Farrell said. Those
with positive scans should still undergo mediastinoscopy; the FDG-PET
images can be used to target lesions to be biopsied by the surgeon.
There remains no consistent workup for staging early NSCLC, and
this study may prove helpful for many patients, said Ned Patz,
MD, professor of radiology, Duke University Medical Center, and a
collaborator on the study.