Robotic stereotactic body radiation therapy for tumors of the liver: radiation-induced liver disease, incidence and predictive factors.

Robotic stereotactic body radiation therapy is a new option to treated unresecable liver tumours. The objectives were to assess the tolerance of this technique, to identify predictive factors for toxicity and evaluate the efficiency of this treatment. From June 2010 to November 2012, robotic stereotactic body radiation therapy was proposed for 56 patients with unresecable hepatocellular carcinomas (23 patients) or hepatic metastases (41 patients). Two or less hepatic lesions, lesion size under 75 mm and WHO score under 3 were selection criteria. The prescribed dose was 45 Gy/3 fractions or 60 Gy/3 fractions. The primary end-point was toxicity, using the radiation-induced liver disease definition and to identify predictive factors. Secondary end-points were in-field local control and overall survival. The median follow-up was 12.5 months. The one-year local control rate and the one-year overall survival rate were 64% [CI95%: 48.2 to 76.5%] and 89% [CI95%: 76 to 95%], respectively. For patient treated with a total dose of 60 Gy, no one experienced recurrence. According to the definition we took, radiation-induced liver disease rate was 0 or 9%. A lesion size at least 35 mm was a predictive factor to liver toxicity (P=0.01). Using robotic stereotactic body radiation therapy, the incidence of radiation-induced liver disease is weak and spontaneously reversible. Prospective studies are required to put in evidence other predictive factors of radiation-induced liver disease and confirm the optimal dose treatment.