In general terms, radiotherapy is treatment of cancer with radiation. With external radiotherapy, the source of the radiation is similar to what creates an X-ray, but with more energy – a high energy x-ray wave. There is also internal radiotherapy, also called brachytherapy. In brachytherapy, a radioactive substance is placed into a tiny pellet or seed, which is placed inside the cancer.Radiation therapy uses high energy particles to kill the cancer cells. The high doses that reach the cancer cells cause damage to their DNA, which prevents the cells from growing and dividing.
When it is delivered externally, the sites are marked on the skin so that the radiation will be aimed at the cancer and not normal tissue. Of course, the radiation has to pass through tissue in between the source and the cancer. But other areas away from the cancer can be protected.
With brachytherapy, the radiation source is inside or next to the cancer. Some irradiation will reach adjacent tissue, but most of the radiation will be limited to the cancer. Brachytherapy is not usually used to treat mesotheliomas.
External radiotherapy, including intensity modulated radiation therapy (IMRT – provide a link)
can be used as the main treatment for mesothelioma in patients whose cancer cannot be treated surgically, or whose general health is not good enough to withstand surgery. It can be used as palliative therapy to decrease symptoms, for example, pain or shortness of breath. Radiotherapy can also be used after surgery to help destroy any cancer cells that may have been left behind.
Before you begin radiotherapy, the radiation therapist will do a process called a simulation with you. The therapist will use a special machine to define your treatment port or field. Your skin will probably be marked. In addition, the therapist may have molds or casts made to help hold your body in exactly the right place.
A schedule for treatment will be set up, because trying to deliver all the necessary radiation to the cancer at one time would cause too much damage to normal cells. The total is divided into fractions, which are smaller doses, and is usually given five days a week, Monday through Friday, for six to eight weeks. This is the most commonly used schedule, but there are others. Your treatment will be tailored for you.
The treatment itself is painless. Side effects usually include skin redness and irritation in the area through which the x-ray beam passes. You can ask your doctor how to treat the area. Generally speaking, you want to protect it from the sun, and avoid anything else that could be irritating to the skin. Use lukewarm water and very mild soap to clean the area. If you have to cover the area, do not put tape over the treatment port.
You will also feel fatigued during radiation therapy. This is due to both the treatment and the cancer.
Other side effects depend on the area treated. If you have pleural mesothelioma, you may have chest symptoms from the radiotherapy, including cough, and shortness of breath. You need to tell your doctor exactly how you are feeling during the therapy. The radiation will eventually improve lung symptoms, decreasing pain and shortness of breath.
Radiotherapy to the abdomen usually causes nausea, vomiting, and diarrhea. There are good medications to help with these symptoms, so be sure and tell your doctor.
You need to eat a healthy diet, and get enough rest during radiotherapy treatment. The therapist can give you specific suggestions about how to handle particular problems. Your doctor supervising the radiation can also help you. Sometimes you may need special advice, for example, from a dietician, to help with specific problems.
Dr. Kaplan
