M e s o t h e l i o m a

A number of refinements and techniques are in use or under study to improve the effectiveness of external radiation therapy. These are described below:
Three-dimensional (3–D) conformal radiation therapy. Traditionally, the planning of radiation treatments has been done in two dimensions (width and height). Three-dimensional (3–D) conformal radiation therapy uses computer technology to allow doctors to more precisely target a tumor with radiation beams (using width, height, and depth). Many radiation oncologists use this technique. A 3–D image of a tumor can be obtained using computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), or single photon emission computed tomography (SPECT). Using information from the image, special computer programs design radiation beams that “conform” to the shape of the tumor. Because the healthy tissue surrounding the tumor is largely spared by this technique, higher doses of radiation can be used to treat the cancer. Improved outcomes with 3–D conformal radiation therapy have been reported for nasopharyngeal, prostate, lung, liver, and brain cancers.
Intensity-modulated radiation therapy (IMRT). IMRT is a new type of 3–D conformal radiation therapy that uses radiation beams (usually x-rays) of varying intensities to deliver different doses of radiation to small areas of tissue at the same time. The technology allows for the delivery of higher doses of radiation within the tumor and lower doses to nearby healthy tissue. Some techniques deliver a higher dose of radiation to the patient each day, potentially shortening the overall treatment time and improving the success of the treatment. IMRT may also lead to fewer side effects during treatment.
The radiation is delivered by a linear accelerator that is equipped with a multileaf collimator (a collimator helps to shape or sculpt the beams of radiation). The equipment can be rotated around the patient so that radiation beams can be sent from the best angles. The beams conform as closely as possible to the shape of the tumor. Because IMRT equipment is highly specialized, not every radiation oncology center uses IMRT.
This new technology has been used to treat tumors in the brain, head and neck, nasopharynx, breast, liver, lung, prostate, and uterus. However, IMRT is not appropriate or necessary for every patient or tumor type. Long-term results following treatment with IMRT are becoming available.