Value of positron emission tomography for lung cancer staging.

OBJECTIVE: The therapeutic strategy in non-small-cell lung cancer (NSCLC) requires exact staging of tumour invasion (T) as well as differentiation between ipsi- and contralateral lymph node invasion (N1/2 vs N3). [18F]FDG-positron emission tomography (FDG-PET) has been shown to detect invaded N with high accuracy while correct determination of T appears to be unclear. The purpose of this prospective study was to evaluate benefit and necessity of 18FDG-PET as an additive to conventional staging modalities. METHODS: Forty patients with suspected non-small-cell lung cancer (NSCLC) were staged by means of computed tomography (CT), bronchoscopy, mediastinoscopy and bone scintigraphy. Additionally, attenuation corrected FDG-PET of the thorax was performed pre-operatively for analysis of T and N topography. After surgical resection with radical lymphadenectomy T and N staging results of CT and PET were compared with the pathological diagnoses. Specificity, sensitivity, positive predictive value and accuracy of CT and PET were calculated. RESULTS: Twenty three squamous cell carcinomas, 14 adenocarcinomas, and three non-malignant tumours were found. Accuracy of CT-T was 0.75 and of PET-T 0.78; accuracy of CT-N was 0.78 and of PET-N 0.80. By combination of CT-T and PET-T accuracy was 0.88. Combination of CT-N and PET-N yielded an accuracy of 0.90. In two out of three cases, PET correctly determined T0. In two cases non-malignant inflammatory lymph nodes were falsely staged as malignant by PET. CONCLUSIONS: Adequate pre-operative T- and N-staging is possible with both CT and FDG-PET. Accuracy can be improved by combination of CT and FDG-PET. FDG-PET is superior to CT in order to differentiate between malignant and benign tumours. However, acute inflammation can mimic malignant lymph node invasion. FDG-PET is justified as a supporting staging measure in cases presenting unclear differentiation between N2 and N3 after conventional staging and is helpful in cases with unclear cell type of the primary tumour.

Improvement of non-small-cell lung cancer staging by means of positron emission tomography.

BACKGROUND: Exact staging of ipsi- and contralateral mediastinal lymph-node metastases (N 1/2 vs. N3) is essential for the therapeutic strategy in non-small-cell lung cancer (NSCLC). CT and mediastinoscopy are the standards of reference for N staging. However, even with these combined measures the extent of invasion of mediastinal lymph nodes can remain vague. 18FDG Positron Emission Tomography (18FDG-PET) has recently been shown to detect invaded nodes with high accuracy. The purpose of this study was to evaluate 18FDG-PET as an aid in N staging. METHODS: 27 patients with suspected NSCLC were clinically staged by means of CT, bronchoscopy, mediastinoscopy, and bone scintigraphy. Additionally, 18FDG-PET was performed preoperatively for analysis of topography of invaded lymph nodes. CT and 18FDG-PET were evaluated in a blinded fashion. Surgical therapy was performed with radical lymphadenectomy. CT N staging as well as PET N staging results were compared with the pathological diagnoses (pTN). Specificity, sensitivity, and accuracy of CT and PET in N staging were calculated. RESULTS: 14 squamous-cell carcinomas, 10 adenocarcinomas, and 3 non-malignant tumors were found. In 8 patients no invasion was found (N0), in 13 patients an ipsilateral invasion (N1/2), and in 3 patients a contralateral invasion (N3). In the correct detection of N1/2 the sensitivity of CT and of PET was 0.77, the specificity of CT and of PET was 0.79. The accuracy of CT was 0.74 and of PET 0.78. By combining CT and PET accuracy was 0.85. CONCLUSIONS: Adequate preoperative LN staging is possible with both CT and 18FDG-PET. The accuracy, however, can be improved by a combination of CT and 18FDG-PET.