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

To report the outcome and toxicity of sequential stereotactic body radiotherapy (SBRT) for multiple liver metastases in patients treated with ExacTrac Adaptive Gating.

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.

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.

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.

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.