Finally, the included literature doesn’t reflect implementation of these newer methods, with only one-quarter of the WY 14643 PPAR inhibitor studies reporting use of 3D-CRT techniques and even less reporting use of IMRT techniques. Nevertheless, this meta-analysis was conducted at an appropriate time, because enough data have accumulated for inspection by meta-analytical methods and we reach the conclusions that reported 3-year and 5-year BFFS, OS and DFS indicated that ART might reduce the need for SRT. We applied multiple strategies to identify studies, strict criteria to include and evaluate the methodological quality of the studies, and subgroup and sensitivity analysis to minimize the heterogeneity. Thus, we provided the most update information in this area. In the tumor microenvironment, hypoxia is one of the crucial factors, which promote an aggressive phenotype of tumor cells and decrease the effectiveness of standard treatment. There are two types of hypoxia: chronic hypoxia, which is associated with an increasing distance of proliferating cells to the vessels, and cycling hypoxia, which is mainly caused by fluctuations in the blood flow rate. The existence of acutely hypoxic cells in tumors was first observed several decades ago and was attributed to transient changes in blood perfusion. These preliminary observations were subsequently confirmed in spontaneous animal tumors, experimental tumors, and in naturally occurring human tumors. Recently, with the usage of pO2-tissue assessment technologies, the existence of cycling hypoxia was directly observed in human tumors. The presence of cycling hypoxia in tumors has direct consequences on the tumor behavior. Cycling hypoxia promotes spontaneous metastasis and the cells exposed to such conditions have even greater metastatic potential than cells exposed to chronic hypoxia. Cycling hypoxia also affects the effectiveness of anticancer therapies, most predominantly radiotherapy. Glioma cells grown both in vitro and as tumor xenografts, preconditioned with application of cycling hypoxia, are more radioresistant. Martinive et al. observed a similar effect for melanoma B16-F10, fibrosarcoma, and hepatocellular cancer cells cultured in vitro. Moreover, it seems that not only transient acute hypoxia affects the behavior of the cells constituting the tumor microenvironment, but also prolonged cycling hypoxia may lead to a selection of cells resistant toapoptosis and standard treatment modalities such as radiotherapy and chemotherapy.