Improvement of Non-Small-Cell Lung Cancer Staging by Means of Positron Emission Tomography

Abstract

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. ¹⁸FDC Positron Emission Tomography (¹⁸FDG-PET) has recently been shown to detect invaded nodes with high accuracy. The purpose of this study was to evaluate ¹⁸FDC-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 ¹⁸FDC-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 ¹⁸FDC-PET. The accuracy, however, can be improved by a combination of CT and ¹⁸FDC-PET.