Gene therapy: A possible aid to cancer radiotherapy.

Extract: Cancer remains a major health problem despite great advances in radiation and other therapeutic modalities. The increasing success of radiotherapy owes to many factors, including the more sophisticated equipment that provides improved treatment techniques and the variety of natural or synthetic subatomic particles available for treatment. This is made possible, in part, by better imaging techniques such as computed tomography (CT, multiple x-rays are combined by computer to give a 2-D image), magnetic resonance imaging (MRI, magnet causes hydrogen atoms to become polarized and their "spin" is measured and summated to create an image of an internal structure), and positron emission tomography (PET, images created of positron decay by radioactive isotopes administered and taken up by the tissue of interest -- in this case the tumor). These new technologies allow one to greatly improve tumor targeting and to better visualize the radiation delivered to all anatomic sites within the patient. All forms of ionizing radiation (radiation that can split atoms and molecules into charged particles and radicals) can destroy any type of cancer cell if a sufficiently high dose is delivered. Normal tissue injury limits the dose of radiation a physician can deliver and thus limits the cancer control rate. Photons (x-ray therapy) are the most common particles used in radiation treatment.