Radiology estimates of viable tumor percentage in hepatocellular carcinoma ablation cavities correlate poorly with pathology assessment

CONTEXT

No study has evaluated radiology/pathology correlation of percentage viable tumor (PVT) estimates in ablated hepatocellular carcinoma (HCC) to examine the reliability of radiologic estimates.

OBJECTIVE

To determine how well interdisciplinary PVT estimates correlate and identify pathologic factors that influence this correlation.

DESIGN

Pathologists and radiologists established blinded PVT estimates in 22 HCC ablation cavities. Paired sample t tests examined the differences between the interdisciplinary estimates.

RESULTS

Fifteen cavities had pathologic viable tumor (VT) (68%) and 6 had radiographic VT (22%). Radiology's sensitivity for detecting VT was 40% and the specificity was 100%. Pathology detected significantly more VT than radiology (pathology mean = 22.3% versus radiology mean = 2.6%; P = .005). Five cavities had tumor growth in a discontinuous rim pattern, 7 in a nodular pattern, and 3 in a solid pattern. Radiology did not detect VT in cavities with a discontinuous rim pattern (sensitivity = 0%) but did detect VT in 3 cavities with a nodular pattern (sensitivity = 43%), and in all cavities with a solid pattern (sensitivity = 100%). There was no significant difference in PVT estimates in cavities 3.5 cm or larger (P = .07), but there was a significant difference in cavities smaller than 3.5 cm (P = .01).

CONCLUSION

This study clarifies that the risk of underestimation by imaging is greatest in small lesions (<3.5 cm), though the sensitivity of detection depends primarily on the tumor growth pattern within the cavity. This underestimation raises the question of whether basing treatment decisions on a radiologic impression of complete ablation is valid.