Apoptosis, Free Radicals and Antioxidant Defense in Antitumor Therapy

Tumor markers are measurable biochemicals that are associated with a malignancy. They are either produced by tumor cells (tumor-derived) or by the body in response to tumor cells (tumor-associated). They are usually substances that are released into the circulation and then measured in the blood sample. There are a few exceptions to this, such as tissuebound receptors that must be measured in a biopsy from the solid tumor or proteins that are secreted into the urine. Despite the fact that tumor markers are hardly ever specific enough to be used alone to diagnose cancer, they do have a number of clinical applications. They can be used to stage cancer, to indicate a prognosis, to monitor treatment, or in follow-up to watch for cancer recurrence. Changes in some tumor markers have been sensitive enough to be used as targets in clinical trials. Tumor markers for diagnosis are used in combination with other clinical parameters such as biopsy and radiological findings. Although there are a multitude of tumor markers, very few of them have found their way into clinical practice because of their lack of specificity. However, some of these non-specific markers have found a place in monitoring cancer treatment rather than in diagnosis.