SBRT as an alternative to RFA for the treatment of primary and metastatic liver tumors.

Abstract

158 Background: Radiofrequency ablation (RFA) is a widely used local therapy for small, unresectable liver tumors (LT). Stereotactic body radiotherapy (SBRT) has been used for similar patients, and has the advantage that it can be used when lesions are adjacent to blood vessels, are difficult to reach and cannot be imaged on ultrasound. We examined RFA and SBRT outcomes for treating primary and metastatic LT at our institution and identified predictive factors for local control. Methods: This study included 62 patients (pts) with 106 LT (69 metastatic, 37 primary) treated with SBRT and 127 pts with 206 LT (80 metastatic, 126 primary) treated with RFA from 2000 to 2010. 42 lesions were ablated intra-operatively while 164 were ablated percutaneously. Mean tumor size by maximum diameter was 2.2 cm (0.4-11) and 2.3 cm (0.6-6.2) for RFA- and SBRT-treated LT, respectively. Freedom from local progression (FFLP) for SBRT was defined as absence of progressive LT within or at the PTV margin while FFLP for RFA was defined as recurrence within or immediately adjacent to the ablation zone. Results: With a median follow-up of 29.4 months (0.46 to 120.8), 1- and 2-yr FFLP rates for all SBRT- vs RFA-treated LT were 93% and 84% vs 86% and 83%. There were 14 cases of residual LT after RFA, 6 of which were re-ablated; these were not counted as RFA failures. Significantly more pts in the SBRT group had received prior systemic therapy (54% vs 31%, p=0.0001) and had active extrahepatic disease at treatment start (36% vs 23%, p=0.01). For SBRT, neither LT size nor dose predicted for FFLP. For RFA, tumor size ≥3 cm had worse FFLP (HR: 5.3, p<0.0001) but an intraoperative approach had better FFLP (HR: −2.2, p=0.01). For tumors >3cm, SBRT had significantly better FFLP than percutaneous RFA (HR: 0.32, p=0.018). In the RFA group, there were 9 complications, including pneumothorax, hemothorax, and small bowel injury, 2 of which resulted in death. In the SBRT group, there was 1 case of radiation-induced liver disease in a Child-Pugh Class B pt but no other significant toxicities. Conclusions: SBRT is a safe alternative to RFA, can be used in a wider variety of patients, and may be more effective than percutaneous RFA at locally controlling larger liver tumors.