Imageable Biomarkers for Radiotherapy Response

Ideally, each patient with a malignancy who is eligible for radiation therapy should receive the most tumoricidal form of this this treatment with the lowest possible risk of toxicity. To overcome radiotherapy resistance, some patients would benefit from a more aggressive approach. This could be treatment intensification, for example by acceleration of the treatment to prevent the negative effects of accelerated tumor cell proliferation, or by boosting certain areas to specifically address intrinsic radioresistance, or a combination of radiotherapy with, for example, a hypoxic cell sensitizer or chemotherapy to reduce the radiotherapy resistance caused by hypoxia. For some patients, one of these approaches can be beneficial but for others could lead to unacceptable side effects. Therefore, it is highly desirable to make the selection upfront. The use of imageable biomarkers could be the key to a more patient-tailored treatment. Different biomarkers for hypoxia and proliferation that could be valuable for radiotherapy are discussed here, including their mechanism, the imaging procedure, quantification, and the value of the results.