Image guided SBRT for multiple liver metastases with ExacTrac® Adaptive Gating

Abstract Aim To report the outcome and toxicity of sequential stereotactic body radiotherapy (SBRT) for multiple liver metastases in patients treated with ExacTrac Adaptive Gating. Background In selected patients with a limited number of liver metastases, SBRT has been evaluated as a safe and effective treatment, with minimal toxicity and high rates of local control. Materials and methods From April 2008 to October 2013, 21 patients with multiple (3–14) liver metastases ( n  = 101) were treated sequentially with SBRT at our institution. Maximum tumor diameter was 7.5 cm. Prior to treatment, internal markers were placed inside or near the tumor. CT or PET-CT simulation was used for the definition of gross tumor volume (GTV). Median planning target volume was 32.3 cc (3.6–139.3 cc). Treatment consisted of 3 fractions (12–20 Gy/fraction) or 5 fractions (10 Gy/fraction), prescribed to the 90–95% of the PTV volume. Daily intra-fraction image guidance was performed with ExacTrac Adaptive Gating. Regular follow-up included CT or PET-CT imaging. Results After a median of 23.2 months, the estimated local control rate was 94.4%, 80.6%, 65% and 65% after 1, 2, 3 and 4 years; the median overall survival was 62 months (95% CI 49.12–74.87) and the actuarial survival reached at 60 months was 57.6%. The univariate data analysis revealed that only primary histology other than colorectal adenocarcinoma was shown as an independent significant prognostic factor for local control ( p  = 0.022). Number of treated metastases did not modify significantly the overall survival ( p  = 0.51). No toxicity higher than G3 (1 patient with chest wall pain) and no radiation-induced liver disease were observed. Conclusions Sequential SBRT with ExacTrac Adaptive Gating for multiple liver metastases can be considered an effective, safe therapeutic option, with a low treatment-related toxicity. Excellent rates of local control and survival were obtained.