Adaptative MR-Guided Stereotactic Body Radiotherapy of Liver Tumors

Hepatic metastases are common in solid cancers (up to 30% of patients with colorectal cancer and up to 50% of patients during their follow-up). The incidence of primary liver cancer increases due to the increase in chronic liver diseases induced by excessive alcohol consumption, hepatitis B and C viruses, and excess fat in the liver. Surgical excision of these liver lesions is the reference treatment but it cannot always be realised. Stereotactic radiotherapy is a recent technique proposed to hepatic metastases treatment from solid cancers and primary hepatic lesions (HCC or cholangiocarcinomas); it is possible to deliver high doses of radiation in the most conformational way possible in order to limit the irradiation of the non-tumor liver. The results of this stereotactic radiotherapy are currently very good with control rates of 75 to 80% at 1 and 2 years with acceptable rates of severe toxicities of 10%. However, the fear of hepatic, digestive (colon, esophagus, stomach) or even cardiac toxicities limits its using to the majority of patients because coupled with a conventional scanner it do not allow direct visualization of the lesion. Due to its non-irradiating nature, MRI guided stereotactic radiotherapy can generate continuous imaging, during the irradiation session, offering " in live " a visualization of the tumor target and organs at risk of proximity. In increasing the precision and safety in the delivery of irradiation, it allows to hope for several areas for improvement of treatment: * reduced uncertainty margins * an increase in the dose delivered * the accessibility of tumor lesions near sensitive organs (esophagus, stomach, heart chambers, intestines, duodenum, right kidney). More, this accelerator allows a re-optimization of the initial dosimetric plan to the anatomical changes of the day to allow an MRI guided adaptive radiotherapy.