Magnetic Resonance Imaging Evaluation of Hepatocellular Carcinoma Treated With Stereotactic Body Radiation Therapy: Long Term Imaging Follow-Up

Purpose: To determine the natural history of imaging findings seen on magnetic resonance imaging (MRI) of hepatocellular carcinoma (HCC) treated with stereotactic body radiation therapy (SBRT). Although arterial hyperenhancement is a key feature of untreated HCC, our clinical experience suggested that tumors that never progressed could still show hyperenhancement. Therefore, we undertook a systematic study to test the hypothesis that persistent arterial phase hyperenhancement (APHE) after SBRT is an expected finding that does not suggest failure of treatment.

Methods and materials: One hundred forty-six patients undergoing SBRT for HCC between January 1, 2007, and December 31, 2015, were screened retrospectively using an institutional review board-approved prospectively maintained registry. Inclusion criteria were (1) HCC treated with SBRT, (2) multiphasic MRI ≤3 months before SBRT, (3) up to 1 year of follow-up MRI post-SBRT, and (4) cirrhosis. The exclusion criterion was ≤3 months of locoregional therapy to the liver segment containing the SBRT-treated HCC. Pre- and post-SBRT MRI from up to 3 years were analyzed in consensus by independent pairs of subspecialty-trained radiologists to determine the temporal evolution of major features for HCC and imaging findings in off-target parenchyma.

Results: Sixty-two patients with 67 HCCs (Organ Procurement and Transplantation Network imaging criteria [OPTN] 5a [n = 26], OPTN 5b [n = 28], OPTN 5x [n = 7]; Liver Imaging Reporting Data System [LI-RAD]-M [n = 4] and LiRADs-4 [n = 2]) were studied. Tumor size either decreased (66% [44 of 67]) or remained unchanged (34% [23 of 67]) within the first 12 months. Post-SBRT APHE was common (58% [39 of 67]). When graded using modified Response Evaluation Criteria in Solid Tumors at 3 to 6 months, 25% (17 of 67) met criteria for complete response and 75% (50 of 67) met criteria for stable disease.

Conclusions: SBRT is an effective locoregional treatment option for HCC. Persistent APHE is common and does not necessarily indicate viable neoplasm; thus, standard response assessment such as modified Response Evaluation Criteria should be used with caution, particularly in the early phases after SBRT therapy.