Currently, researchers are working on a number of refinements to external radiation therapy. These include:

• Three-dimensional (3-D) conformal radiation therapy. This builds on the traditional two-dimensional planning of radiation treatments, which has involved just width and height. Computer technology creates three-dimensional images that also add depth. This allows physicians to more precisely target tumors with beams of radiation that actually conform to the shape of the tumor. The 3-D image of the tumor can be generated using computed axial tomography (CAT), magnetic resonance imaging (MRI), positron emission tomography (PET) or single photon emission computed tomography (SPECT). 

Because this technique is so precise, it largely spares healthy tissues surrounding the tumor from being damaged. Three-dimensional conformal radiation therapy reportedly has been particularly effective in treating nasopharyngeal, prostate, lung, liver and brain cancers and is already in clinical use in many centers.


• Intensity-modulated radiation therapy (IMRT). A new type of three-dimensional conformal radiation therapy that uses radiation beams of varying intensities to deliver different doses of radiation to small areas of tissue at the same time. This results in even greater precision, allowing the physician to deliver higher doses of radiation inside the tumor and lower doses to nearby healthy tissue. A linear accelerator delivers the radiation, and the equipment can be rotated around the patient to ensure that radiation beams are sent from optimal angles. The technology has been used to treat cancers of the brain, head and neck, nasopharynx, breast, liver, lung, prostate, and uterus. Additional research is being conducted on using a combination of this technology with mixed beam radiation therapy (MBRT) to deliver more precise beams to the targeted sites.
  
  
• Stereotatic radiation therapy. Delivers a large dose of radiation precisely to a small tumor area. This is most often used in cancers of the brain, but is also being tried on other types of cancer. Linear accelerators or other machines called gamma knives are used to deliver this treatment. The treatments do not remove the tumors but disrupt the DNA of the tumor cells. The cells are no longer able to reproduce and as a result, the tumors shrink over a period of time. These non-surgical procedures are being used in various medical centers to treat many types of brain tumors.
  
  
• Proton beam radiation therapy. Protons are positively-charged atoms that can be used in beams to radiate tumors. The proton beam may be better for destroying cancer cells while causing less damage to nearby healthy tissues. This type of radiation requires expensive equipment and a specialized staff. For those reasons, there are very few treatment centers in the United States that offer proton beam therapy. In addition, more studies are needed to determine which cancers are best suited for this type of radiation as well as its long-term effectiveness.
  
  
• Intraoperative radiation therapy (IORT). This therapy involves the use of radiation to treat the cancer during surgery. It may be combined with external or internal radiation that is given before or after surgery. Researchers have found IORT to be beneficial to cancers of the abdomen or pelvic region. During IORT, physicians are able to protect nearby normal tissues by moving them out of the targeted radiation beam. IORT is performed in a specialized operating room – one that has been fitted with radiation shields on the surrounding walls.

There are other new approaches to radiation therapy that are being tested. Among the most promising is hyperthermia, which is the use of heat. It is being studied in conjunction with radiation therapy and the combination of treatments appears to increase the effectiveness of radiation on certain tumors.

The use of radiolabeled antibodies also appears to be another promising avenue for radiation treatments. Antibodies are proteins made by the body in response to antigens, which are substances that the immune system recognizes as foreign. Some cancer cells have specific antigens that trigger the production of antibodies specific to tumors. Researchers are developing antibodies and attaching them to radioactive substances that are then injected into the body. Once inside the body, the antibodies seek out the cancer cells, which are then destroyed by the attached radiation. Scientists are also working to develop new radiosensitizers and radioprotectors to increase the effectiveness of radiation and chemotherapy while protecting normal tissues. Some of these drugs are being used in clinical trials for various cancers.

Research is also being conducted on the optimal scheduling and dosages for cancers. For examle, a recent study has found that using intensity-modulated radiation therpay for breast cancer patients may reduce radiation treatment time from six to seven weeks to four weeks.

Studies continue to examine the effectiveness of radiation therapy in conjunction with other treatments, such as biological therapy and surgery. In addition, researchers continue to evaluate the success of radiation therapy in preventing recurrence of cancers and extending survival.