Stereotactic body radiation therapy for liver metastases and primary hepatocellular carcinoma: normal tissue tolerances and toxicity

There is growing interest in stereotactic body radiation therapy (SBRT) as a noninvasive means of treating inoperable hepatic metastases and primary intrahepatic hepatobiliary carcinomas. While initial outcomes are encouraging, the safety of delivering such large, ablative doses is still being studied. We compiled all dose-volume constraints from seven prospective trials of liver SBRT and linked them to reported toxicities. Dose thresholds were made isoeffective, and grade 3 or higher toxicities for liver and adjacent normal tissues were correlated. Four cases of grade 3-5 radiation-induced liver disease (RILD) were identified, including 1 treatment related death, from all patients treated for metastasis. Three of these 4 cases were linked to excessive radiation doses in a large volume of liver. In 56 patients treated for hepatocellular carcinoma (HCC), 1 case of grade 5 RILD and 2 cases of grade 2 hepatic toxicity were reported. Additionally, a prominent retrospective series reported 3 cases of grade 5 RILD in 9 patients treated for HCC. SBRT appears to be safe for treatment of hepatic metastasis. The use of SBRT for HCC should be undertaken with caution or within the context of a clinical trial. Strict adherence to reported dose-volume constraints is advocated.