Advances In Cancer Radiotherapy

An emerging cancer treatment uses what are called monoclonal antibodies to destroy certain types of tumors. These molecules are carefully constructed in laboratories to look and behave like ordinary immune cells, and are designed and programmed to attack the cancer cells directly. They do this in one or more of several ways. Some mark tumors as harmful so that the immune system recognizes the tumor and attacks it, some prevent the growth of blood vessels in the tumor and cut off its oxygen supply, some interfere with the signals that tell the tumor to grow.

Another use of monoclonal antibodies is as the delivery mechanism for radiation treatment. Radiotherapy for cancer works by damaging the cancer cells so that they die off—slowly on cellular time scales, but in a relatively brief time from the patient’s point of view. Though effective, both on its own and in combination with surgery or chemotherapy, the radiation treatments have a high risk of affecting healthy cells as well. While part of the basis for radiation therapy is that healthy tissue is better able to recover from the radiation, it is nonetheless important to minimize the damage to cells not part of the tumor.

With monoclonal antibodies, however, this damage can be avoided. After being introduced into the body, the antibodies go to the site of the tumor and attach to those cells. Because they’re designed, these molecules can be built to deliver a low dose of radiation on an ongoing basis, as opposed to a high dose for a short time—more effective as well as safer—with less inconvenience to the patient and with a reduced risk of harm. The low-dose approach allows the cancer to be attacked relentlessly and completely destroyed. Radioactive particles become inert after a time, and the treatment is administered in such a way that the particles reach this point when the tumor is neutralized or destroyed.

A study in Alabama recently found that combining monoclonal antibodies with safe amounts of radioactive lead was able to destroy tumors without accumulating in the body or damaging ordinary functioning. Further research will look at adjusting the dose to produce the optimal level of radiation.

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