Case of the Month—September 2005

FDG-PET for Staging Lung Cancer

History
A 75-year-old female presented with newly diagnosed non-small-cell lung cancer. A recent CT scan showed a mass in the right lung and mediastinal adenopathy. PET was ordered for further staging for this patient.

Findings
The FDG-PET scan revealed a large focus of intense FDG uptake in the right upper lobe of the lung, which is consistent with the patient’s known cancer. Foci of abnormal uptake in the mediastinum are also present. In addition, there is a focus of intense FDG uptake in the right anterior chest wall (Figure 1B). There was no obvious lesion seen on CT initially. However, when compared side by side, the PET and CT studies reveal a subtle bone lesion that involves the right anterior seventh rib (Figure 1A and Figure 2).


Figure 1a PET scan	Figure 2 CT scan	Figure 1b PET scan

How Did PET Help?
The PET exam identified additional bone metastasis that was not obvious on clinical exam or CT study. The PET finding upgraded the patient’s clinical staging from IIIA to IV.

Discussion
Many studies have demonstrated that FDG-PET is superior to conventional imaging such as CT for staging lung cancer patients. In a patient with lung cancer, PET is useful both to detect extrathoracic metastasis and for mediastinal lymph node staging. Unexpected extratho- racic metastases were detected by PET in 15% of patients in one study1. The negative and positive predictive values were 71 and 83% for mediastinal lymph node staging1.

(1) Lung Cancer: 2004 May; 44(2): 175-81

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