ARRS 2019: Arterial-Phase Hyperenhancement for Hepatocellular Carcinoma Treated With SBRT
Although arterial-phase hyperenhancement is a key feature of untreated or recurrent hepatocellular carcinoma, standard response assessment such as modified Response Evaluation Criteria in Solid Tumors (mRECIST) should be used with caution, particularly in the early phases after stereotactic body radiation therapy (SBRT), so as not to misinterpret treatment response. These were the results of a study presented by Mendiratta-Lala et al at the American Roentgen Ray Society (ARRS) 2019 Annual Meeting (Abstract 1292).
Study Methods
The study was conducted to determine the natural history of imaging findings seen by magnetic resonance imaging (MRI) of hepatocellular carcinoma treated with SBRT, and to test the hypothesis that arterial-phase hyperenhancement following SBRT does not suggest persistent untreated tumor.
A total of 146 patients undergoing SBRT for hepatocellular carcinoma were retrospectively screened for inclusion criteria, which included hepatocellular carcinoma treated with SBRT, multiphasic MRI at 3 months prior to SBRT, minimum 1 year of follow-up MRI after SBRT, and underlying cirrhosis. Exclusion criterion was any patient who underwent locoregional therapy within 3 months to the liver segment containing the SBRT-treated hepatocellular carcinoma. A total of 62 patients with 67 hepatocellular carcinomas were included in the study.
Findings
Within the first 12 months after SBRT, size decreased in 66% of treated tumors and remained unchanged in 34%. After SBRT, 75% of treated hepatocellular carcinomas continued to demonstrate solid arterial phase enhancement, and only 25% were nonenhancing at the time of first follow-up. Of the treated tumors demonstrating arterial enhancement, 58% showed arterial-phase hyperenhancement. Based on these posttreatment enhancement patterns, when graded by mRECIST criteria at 3 to 6 months, 25% met criteria for complete response, and 75% met criteria for stable disease. However, at 1 year, none of the 67 tumors were clinically judged to have local progression.
Study results suggest SBRT is an effective locoregional treatment option for hepatocellular carcinoma and is associated with a low local progression rate. Persistent arterial-phase hyperenhancement is an expected post-SBRT finding and does not indicate viable neoplasm; thus, using standard response assessment classification systems such as mRECIST may lead to a misinterpretation of treatment response, particularly in the early phases after SBRT therapy.
Mishal Mendiratta-Lala, MD, first author of the study, said, “The results of this research are extremely exciting, as it will significantly impact clinical care. Historically, [arterial-phase hyperenhancement] seen in hepatocellular carcinoma treated with SBRT has been interpreted as viable disease, and patients have undergone repeat treatments. However, our results, as well as a few additional studies from our institution, suggest that these lesions are nonviable, and thus, these patients do not need to undergo additional treatments, and can even be eligible for transplant.”
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