Long-Term Results of a Phase 1 Dose-Escalation Trial and Subsequent Institutional Experience of Single-Fraction Stereotactic Ablative Radiation Therapy for Liver Metastases

We report long-term outcomes from our phase 1 dose-escalation study to determine the maximum tolerated dose of single-fraction liver SABR pooled with our subsequent single institutional experience with patients treated postprotocol at the highest dose level (40 Gy) established from the phase 1 study.Patients with liver metastases from solid tumors located outside of the central liver zone were treated with single-fraction SABR on a phase 1 dose escalation trial. At least 700 cc of normal liver had to receive9.1 Gy. Seven patients with 10 liver metastases received the initial prescription dose of 35 Gy, and dose was then escalated to 40 Gy for 7 more patients with 7 liver metastases. An additional 19 postprotocol patients with 22 liver metastases were treated to 40 Gy in a single fraction. Patients were followed for toxicity and underwent serial imaging to assess local control.Median imaging follow-up for the combined cohort (n = 33, 39 lesions) was 25.9 months; 38.9 months for protocol patients and 20.2 months for postprotocol patients. Median lesion size was 2.0 cm (range, 0.5-5.0 cm). There were no dose-limiting toxicities observed for protocol patients, and only 3 grade 2 toxicities were observed in the entire cohort, with no grade ≥3 toxicities attributable to treatment. Four-year actuarial local control of irradiated lesions in the entire cohort was 96.6%, 100% in the protocol group and 92.9% in the subsequent patients. Two-year overall survival for all treated patients was 82.0%.For selected patients with liver metastases, single-fraction SABR at doses of 35 and 40 Gy was safe and well-tolerated, and shows excellent local control with long-term follow-up; results in subsequent patients treated with single-fraction SABR doses of 40 Gy confirmed our earlier results.