Stereotactic body radiotherapy-induced arterial hypervascularity of non-tumorous hepatic parenchyma in patients with hepatocellular carcinoma: potential pitfalls in tumor response evaluation on multiphase computed tomography.

Abstract

PURPOSE: To evaluate temporal changes in contrast enhancement patterns of

non-tumorous hepatic parenchyma with a focus on arterial hypervascularity on

multiphase computed tomography (CT) in patients with hepatocellular carcinoma

(HCC) treated with stereotactic body radiotherapy (SBRT). METHODS: We

retrospectively identified 61 patients who had undergone multiphase

contrast-enhanced CT at one, three, and six months after SBRT. Irradiated versus

non-irradiated liver parenchyma was delineated by cross-correlation with the

dose-volume histogram of SBRT plan. Serial changes in the contrast enhancement

patterns of the irradiated versus non-irradiated liver parenchyma were evaluated

by two abdominal radiologists in consensus. We compared the frequency of the

contrast enhancement patterns according to the follow-up period using the

Fisher-Freeman-Halton exact test. RESULTS: The irradiated non-tumorous hepatic

parenchyma showed that the prevalence of arterial hypervascularity increased

during the follow-up period (P<.01): 11.5% (7/61) in one, 45.9% (28/61) in three,

and 54.1% (33/61) in six months. Contrast wash-out on the delayed phase was

uncommon: 1.6% (1/61) in one, 3.3% (2/61) in three, and 0% in six months.

CONCLUSION: The incidence of arterial hypervascularity of the irradiated hepatic

parenchyma gradually increased until six months after SBRT, which could interfere

with the accurate evaluation of treatment response. The lack of wash-out on the

delayed phase in the hypervascular area would distinguish SBRT-related change

from residual/recurred HCC.