[Stereotactic body radiation therapy in the management of liver tumours]

Single high dose irradiation induces cell cycle arrest and apoptosis in human hepatocellular carcinoma cells through the Ras/Raf/MEK/ERK pathways

Purpose: Stereotactic body radiation therapy (SBRT) is emerging as a new noninvasive treatment in patients with primary liver carcinoma or liver-confined metastatic cancer. However, the radiobiological targets remain a subject of debate. Here, we investigated the potential biological effects of the radiation on the human hepatocellular carcinoma HepG2 cells.Materials and methods: Firstly, HepG2 cells were divided into three groups: control group, 3.5 Gy*8f group (L group), and 15 Gy*1f group (H group). After treatment, cell proliferation was examined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide and plate colony formation assays. Cell cycle and apoptosis were assessed using propidium iodide and Hoechst 33258 staining, respectively. Furthermore, the mechanisms underlying irradiation-induced cell cycle arrest and cell apoptosis were investigated by Western blot assay.Results: Irradiation could effectively inhibit the proliferation and colony formation of HepG2 cells, and the single high dose irradiation showed stronger inhibitory effects. Irradiation-induced cell cycle arrest at G2/M phase in HepG2 cell, during which the expression levels of cyclin B1, CDK1, and p-CDK1 proteins were downregulated, whereas expression of p21 was upregulated in the irradiated HepG2 cells. After irradiation, typical morphological changes of apoptosis in HepG2 cells were observed; the number of cell apoptosis and the expression of apoptosis associated proteins were significantly increased in HepG2 cells by high dose irradiation compared with low dose irradiation. Additionally, compared with low dose irradiation, high dose irradiation significantly downregulated the phosphorylated proteins in the Ras/Raf/MEK/ERK signaling pathway.Conclusions: Our results suggest that irradiation applied in SBRT, particularly single high dose irradiation, mediates its anti-tumor effects by inducing cell cycle arrest and apoptosis via modulation of the Ras/Raf/MEK/ERK signaling pathway.

[Stereotactic body radiotherapy for liver tumors: State of the art]

Thanks to the improvement in radiotherapy physics, biology, computing and imaging, patients presenting with liver tumors can be efficiently treated by radiation. Radiotherapy has been included in liver tumors treatment guidelines at all disease stages. Liver stereotactic radiotherapy has to be preferred to standard fractionated radiotherapy whenever possible, as potentially more efficient because of higher biological equivalent dose. Liver stereotactic radiotherapy planning and delivery require extensive experience and optimal treatment quality at every step, thus limiting its availability to specialized centres. Multicentre studies are difficult to develop due to a large technical heterogeneity. Respiratory management, image guidance and immobilization are considerations as important as machine type. The use of multimodal planning imaging is compulsory to achieve expected contouring quality. Treatment efficacy is difficult to assess following liver stereotactic radiotherapy, but local control is high and toxicity unusual. As a consequence, liver stereotactic radiotherapy is part of multimodal and multidisciplinary management of liver tumors.

Management of liver cancer. The Surgeon's point of view

During the last twenty years, a huge progress has been achieved in the treatment of liver cancer and recent strategies include interventional radiology, chemotherapy regimens and surgery. Meanwhile, Stereotactic Body Radiation Therapy (SRBT) has developed in the treatment of all organs with millimetre accuracy, very few side effects and a high control rate. So, SRBT has become a therapeutic weapon in his own right in liver tumour treatment. Many publications have reported encouraging results in colorectal liver metastasis, hepatocellular carcinoma on cirrhosis and peripheric cholangiocarcinoma. It is important that radiation therapists involve systematic multidisciplinary "liver tumour" meetings to discuss therapeutic indications and initiate treatments quickly.

[Strategy for technical evaluation in radiation oncology: methodological and ethical aspects, the French society for radiation oncology's opinion]

Evidence-based medicine is a paradigm founded on a hierarchy of research design, accepted as a dogma. Applied to radiation oncology, and specifically to radiotherapy technical comparisons, evidence-based medicine implies methodological and ethical problems. The concept of "incremental" evolution and the dosimetric evidence are proposed as an acceptable alternative to comparative clinical trials if total dose, time, fractionation, and target volumes are not modified. For other situations, either randomized comparative trials or observational studies are needed. When randomized comparative trials are not possible, observational studies, whose validity can be enhanced by appropriate methodology, must be considered as a valid method.