Correlation of 18F-fluorodeoxyglucose Uptake on Positron Emission Tomography with Ki-67 Index and Pathological Invasive Area in Lung Adenocarcinomas 30 Mm or Less in Size

Background: (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) is commonly used to distinguish benign from malignant lesion. Recently, maximum standardized uptake value (SUVmax) on FDG-PET has found to have prognostic value. We examined the relationship between SUVmax and proliferative activities as indicated by maximum diameter of tumor opacity on mediastinal-window images (TOM), Ki-67 index, and diameter of the pathological invasive area in lung adenocarcinomas <or=30 mm.

Methods: Thin-section computed tomography (TS-CT) and FDG-PET were performed on 140 patients with resectable lung adenocarcinomas <or=30 mm between March 2006 and May 2008. Tumors were classified as air-type or solid-type based on TS-CT findings. In all resected specimens, diameter of the pathological invasive area and Ki-67 index were assessed.

Results: SUVmax was significantly lower for air-type than for solid-type tumors (0.97 vs. 3.96, p<0.0001). In solid-type tumors, SUVmax correlated with diameter of TOM (r=0.450, p<0.0001), Ki-67 index (r=0.567, p<0.0001), and diameter of the pathological invasive area (r=0.672, p<0.0001). In multiple regression analysis, SUVmax correlated significantly with Ki-67 index and diameter of the pathological invasive area but not with diameter of TOM. The cut-off value of SUVmax for predicting invasive area >5mm was determined as 2.15 by ROC analysis, with sensitivity of 88.3% and specificity of 84.6%.

Conclusions: SUVmax correlated significantly with Ki-67 index and diameter of the pathological invasive area. The present results suggest the potential role of FDG-PET in predicting adenocarcinomas with invasive characteristics.