Radiation Therapy to Treat Cancer
Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. At low doses, radiation is used in x-rays to see inside your body, as with x-rays of your teeth or broken bones.
How Radiation Therapy Works Against Cancer
At high doses, radiation therapy kills cancer cells or slows their growth by damaging their DNA. Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and removed by the body.
Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before DNA is damaged enough for cancer cells to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.
Types of Radiation Therapy
There are two main types of radiation therapy, external beam and internal.
The type of radiation therapy that you may have depends on many factors, including:
- The type of cancer
- The size of the tumor
- The tumor’s location in the body
- How close the tumor is to normal tissues that are sensitive to radiation
- Your general health and medical history
- Whether you will have other types of cancer treatment
- Other factors, such as your age and other medical conditions
External Beam Radiation Therapy
External beam radiation therapy comes from a machine that aims radiation at your cancer. The machine is large and may be noisy. It does not touch you, but can move around you, sending radiation to a part of your body from many directions. External beam radiation therapy is a local treatment, which means it treats a specific part of your body. For example, if you have cancer in your lung, you will have radiation only to your chest, not to your whole body.
Internal Radiation Therapy
Internal radiation therapy is a treatment in which a source of radiation is put inside your body. The radiation source can be solid or liquid.
Types of Cancer that Are Treated with Radiation Therap:
External beam radiation therapy is used to treat many types of cancer.
Internal radiation therapy is often used to treat cancers of the head and neck, breast, cervix, prostate, eye, and certain types of thyroid cancer.
How Radiation Is Used with Other Cancer Treatments:
For some people, radiation may be the only treatment you need. But, most often, you will have radiation therapy with other cancer treatments, such as surgery, chemotherapy, and immunotherapy. Radiation therapy may be given before, during, or after these other treatments to improve the chances that treatment will work. The timing of when radiation therapy is given depends on the type of cancer being treated and whether the goal of radiation therapy is to treat the cancer or ease symptoms.
When radiation is combined with surgery, it can be given:
- Before surgery, to shrink the size of the cancer so it can be removed by surgery and be less likely to return.
- During surgery, so that it goes straight to the cancer without passing through the skin. Radiation therapy used this way is called intraoperative radiation. With this technique, doctors can more easily protect nearby normal tissues from radiation.
- After surgery to kill any cancer cells that remain.
Lifetime Dose Limits:
There is a limit to the amount of radiation an area of your body can safely receive over the course of your lifetime. Depending on how much radiation an area has already been treated with, you may not be able to have radiation therapy to that area a second time. But, if one area of the body has already received the safe lifetime dose of radiation, another area might still be treated if the distance between the two areas is large enough.
Radiation Therapy Can Cause Side Effects:
Radiation not only kills or slows the growth of cancer cells, it can also affect nearby healthy cells. Damage to healthy cells can cause side effects.