Compared to conventional radiotherapy, using avidin and biotin to pre-target tumors with radio-immunotherapy demonstrably improves the uptake of radiation by malignant tissue. A study of pre-targeted radio-immunotherapy in patients with non-Hodgkin's lymphoma using streptavidin, the antibody Rituximab, and radioactively tagged biotin (
An obstacle to using radio-immunotherapy in lymphoma cancer patients is the toxicity caused by radioactively labeled antibodies that are absorbed in organs. However, research has demonstrated that using avidin and biotin to pre-target the tumor also permits screening out radioactive antibodies still circulating in the blood, thus limiting the amount absorbed by these organs.38 One way to remove these non-tumor bound radioactive molecules is by administering a clearing agent (either biotin or avidin-based) that binds to and removes them from circulation.38-39
Another option is extracorporeal affinity adsorption treatment (ECAT). After the tumor shows uptake of the antibodies, the patient's blood is circulated out and over an avidin-coated filter - returning virtually antibody-free blood to the body. This allows higher radiation dosages and a greater tumor absorption rate, especially beneficial for patients who have failed to respond to standard treatments. In one study involving eight such patients - with lymphoma non-responsive to standard treatment - all treated were able to tolerate higher doses. The eight patients (seven with aggressive or mantle cell B-cell lymphoma) also achieved tumor uptake at the higher radiation infusions. With less organ absorption of the radioactive antibodies in the blood, body, lungs, liver, and kidneys, seven of the eight patients were able to continue with radio-immunotherapy/ECAT treatment with no adverse effects during the procedure.39
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A protein in egg whites.9
A molecule of short half-life radioactive yttrium that emits beta particles (energetic electrons) bound to a biotin molecule.38