18F-FDG PET for the lymph node staging of non-small cell lung cancer in a tuberculosis-endemic country: is dual time point imaging worth the effort?

Abstract

This study was to compare (18)F-FDG positron emission tomography (PET) with thoracic contrast-enhanced CT (CECT) in the ability of lymph node (LN) staging non-small cell lung cancer (NSCLC) in a tuberculosis-prevalent country. The usefulness of dual time point PET imaging (DTPI) in NSCLC nodal staging was also evaluated. We reviewed 96 NSCLC patients (mean age, 65.3+/-11.7 years) who had received PET studies before their surgery. DTPI were performed on 37 patients (mean age, 64.8+/-12.2 years) who received an additional scan of thorax 3 h after tracer injection. The accuracies of nodal staging by CECT and PET were evaluated according to final histopathology of hilar and mediastinal LN resected by surgery. The accuracy for nodal staging by CECT was 65.6% and that by PET was 82.3% (p<0.05). Six patients were over-staged and 11 were under-staged by PET. Tuberculosis (n=3, 50%) were mostly responsible for false-positive, while small tumor foci (n=7, 63.6%) were mostly accountable for false-negative. For the 37 patients with DTPI, 45 min standardized uptake value (SUV) and 3 h SUV for negative LNs are significantly lower than those for positive LNs (p<0.0001). Nevertheless, the retention index (RI) showed no significant difference between these two groups. Our study demonstrates that PET is more accurate than CECT in LN staging NSCLC patients in Taiwan where TB is still prevalent. Semi-quantitative SUV method or DTPI with RI does not result in better diagnostic accuracy than visual analysis of PET images.