Analysis of FDG uptake pattern for early evaluation of response to transarterial chemoembolization (TACE) in nodular hepatocellular carcinoma

Abstract

Objectives: To compare FDG PET/CT findings in nodular hepatocellular carcinoma (HCC) for early evaluation of therapeutic response to TACE. Methods FDG PET/CT performed on patients with nodular HCC(≥2cm) within the 3 months after TACE from Feb. 2006 to July 2009. Tumor viability was confirmed by surgery or follow-up TACE, or the CT, MRI at least 3 months after TACE. PET/CT of 37 patients (mean age 59.8 yrs,time intervals 15.9±2.7 days) were selected. FDG uptake patterns of the lesions were classified into no uptake, focal uptake, even marginal uptake, uneven marginal uptake and diffuse uptakes. We analyzed PET using three positive criteria based on uptake pattern (criteria 1, all uptake; criteria 2, focal or marginal uptake; criteria 3, focal or uneven marginal uptake).

Results: Of 47 lesions, viable tumors were observed in 18 lesions. Viable tumor was significantly larger than those of non-viable tumor (5.6±0.9 cm vs. 3.1±0.2 cm, p<0.001). False positive results occured in 10 lesions (4 diffuse, 4 uneven marginal, 2 focal) and false negative results occured in 4 lesions. Almost false positive PET/CT studies (9/10) were observed within a week interval. The shorter intervals, the more diffuse uptake were observed (spearman, Rho=-4.63, p<0.001). Sensitivity of PET using Criteria 3 was lower than those of applying Criteria 1 and Criteria 2(38.9%,77.8%,77.8%, p<0.05). Specificity was similar applying three criteria(65.5%, 79.3%, 79.3%).

Conclusions: The results suggest there should be some caution in assessing FDG PET to evaluate therapeutic response of TACE in terms of diffuse increased uptake patterns and short time intervals after TACE