Phase I study of individualized stereotactic body radiotherapy of liver metastases.

Purpose: To report on the outcomes of a phase I study of stereotactic body radiotherapy (SBRT) for treatment of liver metastases.
Patients and Methods: Patients with liver metastases that were inoperable or medically unsuitable for resection, and who were not candidates for standard therapies, were eligible for this phase I study of individualized SBRT. Individualized radiation doses were chosen to maintain the same nominal risk of radiation-induced liver disease (RILD) for three estimated risk levels (5%, 10%, and 20%). Additional patients were treated at the maximal study dose (MSD) in an expanded cohort. Median SBRT dose was 41.8 Gy (range, 27.7 to 60 Gy) in six fractions over 2 weeks.
Results: Sixty-eight patients with inoperable colorectal (n = 40), breast (n = 12), or other (n = 16) liver metastases were treated. Median tumor volume was 75.2 mL (range, 1.19 to 3,090 mL). The highest RILD risk level investigated was safe, with no dose-limiting toxicity. Two grade 3 liver enzyme changes occurred, but no RILD or other grade 3 to 5 liver toxicity was seen, for a low estimated risk of serious liver toxicity (95% CI, 0 to 5.3%). Six (9%) acute grade 3 toxicities (two gastritis, two nausea, lethargy, and thrombocytopenia) and one (1%) grade 4 toxicity (thrombocytopenia) were seen. The 1-year local control rate was 71% (95 CI, 58% to 85%). The median overall survival was 17.6 months (95% CI, 10.4 to 38.1 months).
Conclusion: Individualized six-fraction liver metastases SBRT is safe, with sustained local control observed in the majority of patients.