Phase II trial on SBRT for unresectable liver metastases: long-term outcome and prognostic factors of survival after 5 years of follow-up

Background: The aim of this study was to evaluate long-term efficacy and survival prognostic factors of stereotactic body radiation therapy (SBRT) for un-resectable liver metastases in patients enrolled in a prospective phase II trial. Methods and materials: 5-year local control (LC), overall survival (OS), progression free survival (PFS) and toxicity rates were analyzed in patients with un-resectable liver metastases enrolled in a Phase II Trial on liver SBRT, with a prescription dose of 75Gy in 3 consecutive fractions. Results: A total of 61 patients with 76 lesions were enrolled, with a median follow-up time of 6.1 years. One, three and 5 year LC rates were 943.1%, 78.0 +/- 5.9% and 78.0 +/- 5.9%, without reaching the median LC time. Median OS was 27.6months and the survival rates were 85.2 +/- 4.5%, 31.1 +/- 5.9% and 18.0 +/- 4.9% at 1, 3 and 5-year after SBRT, respectively. Univariate analysis showed that favorable primary site (colorectal, breast and gynecological) of metastases (p = 0.001) improved survival. Toxicity was moderate. One patient experienced G3 late chest wall pain, which resolved within 1 year from SBRT. No cases of Radiation Induced Liver Disease (RILD) were detected. Conclusions: Long-term results of this Phase II study suggest the efficacy and safety of SBRT for un-resectable liver metastases after 5-year of follow up. Selection of cases with positive prognostic factors may improve long-term survival of these oligo-metastastic patients and may confirm the role of SBRT as an effective alternative local therapy for liver metastases.