Mee Jin Park MD, Presenter: Nothing to Disclose

So Yeon Kim MD, Abstract Co-Author: Nothing to Disclose

Hyung Jin Won MD, Abstract Co-Author: Nothing to Disclose

Sang Min Yoon, Abstract Co-Author: Nothing to Disclose

Seong Ho Park MD, Abstract Co-Author: Nothing to Disclose

Seung Soo Lee MD, Abstract Co-Author: Nothing to Disclose

Yong Moon Shin, Abstract Co-Author: Nothing to Disclose

Pyo Nyun Kim MD, Abstract Co-Author: Nothing to Disclose

Moon-Gyu Lee MD, Abstract Co-Author: Nothing to Disclose

Stereotactic body radiation therapy (SBRT) has emerged as a promising therapy for patients with inoperable hepatocellular carcinoma (HCC). The differences in the delivered radiation dose as well as the complex dose distribution of SBRT would cause substantial differences in radiologic appearance compared to conventional radiotherapy. The purpose of this study is to evaluate temporal changes in contrast enhancement patterns on multiphase CT and volume of non-tumorous hepatic parenchyma in patients with HCC treated with SBRT.

We retrospectively identified 61 patients (52 men, 9 women; mean age, 61.7 years) who underwent multiphase contrast-enhanced CT at one, three, and six months after SBRT with a total dose of 36-60 Gy per 3 or 4 fractions. Irradiated versus non-irradiated liver parenchyma was delineated in each patient by cross-correlation with the dose-volume histogram of SBRT treatment plan. Serial changes in contrast enhancement patterns and volume of the irradiated versus non-irradiated liver parenchyma were evaluated by two abdominal radiologists in consensus. The Fisher exact test was used to analyze the prevalence of changes in contrast enhancement patterns and volume in the irradiated and non-irradiated liver parenchyma over the follow-up period.

The irradiated non-tumorous hepatic parenchyma showed the prevalence of arterial hypervascularity increased with follow-up duration (P<.01): 11.5 % (7/61) in 1-month, 45.9% (28/61) in 3-month, and 54.1 % (33/61) in 6-month follow-up CT. Contrast wash-out (hypoattenuation) at the delayed phase was uncommon across the follow-up periods: 1.6% (1/61) in 1-month, 3.3 % (2/61) in 3-month, and 0% in 6-month follow-up CT. On the other hand, reduction in volume of the irradiated area was increasingly noted with follow-up duration (P<.01): 3.3% (2/61) in 1-month, 52.5% (32/61) in 3-month, and 88.5% (54/61) in 6-month follow-up CT.

After SBRT, post-radiotherapy arterial hypervascularity of non-tumorous hepatic parenchyma was increasingly present in follow-up CT. Lack of wash-out at the delayed phase and concomitant decrease in volume would help differentiate radiation-induced arterial hypervascularity from residual HCC.

Post-radiotherapy arterial hypervascularity after SBRT is common and should be considered to accurately assess tumor treatment response of HCC on multiphase CT.

Park, M, Kim, S, Won, H, Yoon, S, Park, S, Lee, S, Shin, Y, Kim, P, Lee, M, Stereotactic Radiotherapy-induced Arterial Hypervascularity of Non-tumorous Hepatic Parenchyma in Patients with Hepatocellular Carcinoma: Potential Pitfalls in Tumor Response Evaluation on Multiphase CT.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043461.html