Radiation therapy for mesothelioma involves the use of high-energy x-rays to kill cancerous cells. Radiation therapy is typically used for patients who are not healthy enough to sustain more extensive types of surgery or it may be used for patients who have received surgery and want to prevent mesothelioma from spreading to the area of the surgical incision or to kill cancer deposits that were missed during surgery. There are four primary types of radiation therapy in use for mesothelioma; they include external beam, adjuvant and palliative radiation therapy as well as brachytherapy.  Radiation therapy offers side effects, such as fatigue and skin changes that are similar to sunburn. These side effects are usually temporary. However, radiation therapy may also cause side effects of mesothelioma to worsen. These effects may not be so temporary. Side effects of radiation therapy in the area of the chest may lead to increased shortness of breath, difficulty breathing and it may expose other sensitive organs to the radiation. The heart, lungs and spinal cord have the potential to be affected and most doctors will reduce the level of radiation to an amount that is less than the level that would otherwise be used in an effort to protect these sensitive organs. This is thought to contribute to the ineffectiveness in radiation therapy. The side effects of radiation therapy in the area of the abdomen may lead to increased nausea, vomiting and diarrhea. External beam radiation therapy involves the use of radiation as delivered from outside of the body and directed to the cancer it is expected to kill. Though this type of radiation has been used traditionally to treat mesothelioma as well as other forms of cancer, it has not proven to be very effective in treating mesothelioma. The procedure is simple. It is similar to receiving the type of diagnostic x-ray that most people are accustomed to. The difference for external beam x-rays is that the x-rays are given for a longer period of time. Typical external beam radiation therapy is provided for 3 to 5 weeks with treatment for 5 days of each of the weeks. Mesothelioma has proven to be resistant to this traditional method of radiation therapy and when the lungs contain the targeted cancer of interest, x-rays may create additional damage to the lungs. Adjuvant radiation therapy is usually used to complement surgery for mesothelioma. Radiation is targeted to small deposits of cancer that were undetected or otherwise not removed during surgery. Palliative radiation therapy is used to relieve the symptoms of mesothelioma, but it is not likely to kill all existing cancer. Palliative radiation therapy may assist patients who are in pain or suffering any number of other complications that may affect their quality of life. 

Brachytherapy provides a method of internal radiation. Radioactive material is placed within the body at the site of cancer to kill cancer cells. This type of procedure is risky and rarely used to treat mesothelioma. When it is used for pleural mesothelioma, where fluid build up has been removed, radioactive drugs are put into the space that was occupied by the fluid. In some cases, this procedure has been effective in preventing any further build up of fluids.