Linac based radical radioablation of liver tumors.

Due to the low percentage of resectable liver tumors, new alternative treatment modalities are used. Among them, radioablation, that is, by using a limited number of high dose radiation. The aim of this study was to evaluate the effectiveness of liver tumor radioablation at 36 Gy delivered in three fractions. The analyzed material comprised of 65 liver tumors. In 61 cases, we irradiated metastases (20 rectal cancers) and in 4 primary liver tumors. Radioablation, was done using 6 and 20 MV photons with a fraction dose of 12 Gy once a week up to a total dose of 36 Gy. During the follow-up we measured tumor diameters, and for our statistics we used a classical linear regression and the Bayesian approach. Mild and moderate late toxicity was observed. We found a significant absolute and relative decrease in tumor size during the first 6 months from the whole analyzed group. In subgroups with adenocarcinomas, metastases of gastrointestinal tract (GI) cancers, metastases of cancers other than GI cancers, and in the subgroup in which 2D-2D kV system (IGRT) and respiratory gating was used. The percentage of tumors with local control (lack of "in field" progression) after 6 months was 89%. The obtained results permit us to conclude that gated SBRT of liver tumors is an effective and safe treatment modality resulting in a significant regression of liver tumors and that the highest degree of tumor size reduction can be expected for metastases of non-gastro intestinal tract cancers.