Purpose: To examine whether dexamethasone suppression can reduce fluorine 18 fluorodeoxyglucose (FDG) uptake in false-positive (FP) findings in pulmonary and mediastinal lymph nodes in non-small cell lung cancer (NSCLC).
Materials and methods: Institutional ethics review board approved this prospective study with written informed consent. The study population was composed of 17 patients with NSCLC who underwent both baseline and dexamethasone suppression (24 hours after oral administration of 8 mg dexamethasone) FDG positron emission tomography/computed tomography and surgery. FDG uptake was evaluated by using a five-point visual scoring system (negative findings, score of 0-1; positive findings, score of 2-4) and maximum standardized uptake value (SUVmax). The Mann-Whitney U, Wilcoxon signed-rank, Kruskal-Wallis, or Spearman rank correlation tests were used as necessary for statistical evaluations.
Results: In 17 primary lesions, no significant difference was noted in visual score between baseline (mean, 3.4 ± 1.2) and dexamethasone suppression scans (mean, 3.3 ± 1.2; P = .16), although SUVmax was significantly lower on dexamethasone suppression scans (mean, 7.1 ± 5.2) than on baseline scans (mean, 8.6 ± 6.6; P = .005). In eight nodes with true-positive (TP) findings, there were no significant differences in visual score (mean for both, 3.8 ± 0.5) and SUVmax (mean, 5.3 ± 2.3 vs 5.5 ± 2.5, respectively; P = .81) between baseline and dexamethasone suppression scans. In 19 nodes with FP findings at baseline, dexamethasone suppression resulted in significantly lowered visual score (mean, 3.4 ± 0.6 vs 2.4 ± 0.8, respectively; P < .001) and SUVmax (mean, 3.5 ± 0.8 vs 2.7 ± 0.7, respectively; P < .001), and four nodes with FP findings were rated as true-negative findings on dexamethasone suppression scans, which resulted in a significant difference in SUVmax between nodal lesions with TP and FP findings (P = .014).
Conclusion: Oral dexamethasone has the potential to reduce FDG uptake in pulmonary and mediastinal nodes with FP findings in NSCLC.