Chemoradiotherapy for Patients With Oligometastatic Colorectal Cancer

Combining chemoradiation with an antiangiogenic agent has a strong biological rationale, and preclinical studies consistently show an increase in radiosensitization with combined treatment. It is well described that hypoxia or HIF-1 expression is associated with a lower radiation response and progression in solid tumors. Radiation itself induces transient tumor hypoxia, which in turn stimulates VEGF production and VEGFR-2 expression what may also serve as a paracrine proliferative stimulus that promotes out-of-field growth. The combination of radiotherapy with an antiangiogenic agent (e.g. bevacizumab) thus offers the potential to enhance the effect of radiation, and avoid further spread of disease. Furthermore, targeting tumor vasculature improves the delivery of cytotoxic drugs (e.g. capecitabine) leading to increased efficacy of chemoradiation. Combination with cytotoxic drugs could additionally limit treatment-induced hypoxia (Senan and Smit 2007; Mazeron, Anderson et al. 2011).