Radiation comes from atoms, the building blocks of matter. Everything that exists in the universe — planets, stars, minerals, plants, and all living things — consists of atoms.

In the late 1800s, scientists discovered that a few atoms are unstable. Unstable atoms contain excess energy, which means that they may undergo a spontaneous change or reaction, releasing energy into the environment. Some of the energy that unstable atoms release is radiation.

It wasn’t long before scientists found ways to harness radioactive energy and began exploring its effects on human cells. Among the pioneers in this field were Henri Becquerel, Wilhelm Roentgen, Pierre Curie, and Marie Curie, the two-time Nobel prize winner.

One of their early, important insights into radiation was that, while it could be damaging to healthy tissue in high doses, it was especially lethal to cancer cells. Scientists soon began treating malignant tumors with radiation.

Radiation therapy

The power of radiation energizes the fight against cancer.

About 60% of all people with cancer have radiation therapy. If you’re one of them, it may be your primary treatment, or you may receive it in combination with another therapy, such as surgery or chemotherapy. For example, radiation is often used to eliminate any cancer cells that may remain after surgery or to shrink a tumor before surgery to make the procedure less extensive. Radiation may also be used palliatively, or to ease pain associated with cancer.

New techniques combining radiation therapy with advances in physics, biology, and computer engineering are constantly evolving that improve the effectiveness of radiation while limiting its impact on healthy tissue.

How radiation works

Radiation is energy in the form of heat or light that travels through space. Sunlight is one of the many forms of radiation. X-rays that your doctors and dentists use during routine medical exams are another.

In radiation therapy, high-energy X-rays — similar to what your doctor or dentist uses, but much more powerful — are directed at the tumor. The radiation damages the DNA and other structural aspects of the cancer cells. This either kills the cells immediately or weakens them so that they cannot reproduce.

External beam radiation

Most people who are treated with radiation receive some form of external beam radiation therapy, or EBRT. The procedure is similar to having an X-ray taken, though it lasts for one to five minutes rather than just a few seconds. The treatments themselves are painless, and you will not feel orsee the radiation, although you may experience side effects after treatment. People receiving external radiation are not radioactive, and pose no danger of exposing others to radiation.

Internal radiation

In some cases, cancer can be treated most effectively using internal radiation. For this treatment, the radioactive material is placed inside your body. You may receive internal radiation in the form of radioactive implants, through an IV or catheter, or orally, as a pill or liquid.

Brachytherapy is a form of internal radiation commonly used to treat localized tumors. Tiny radioactive wires or pellets are implanted near or within the tumor, where they give off radiation for several days or weeks. Studies suggest that brachytherapy may be just as effective as surgery. In addition, it has fewer side effects than EBRT, such as burns or skin irritation. However, brachytherapy is not appropriate for everyone, so it’s smart to discuss other forms of radiation treatment with your oncologist.

Side effects

Because radiation therapy is a localized treatment, its side effects are usually limited to the tumor area. The majority are temporary and can often be relieved with medication and natural therapies your doctors prescribe. Here are some of the most common:

Fatigue is a common side effect of radiotherapy. Good nutrition, adequate rest, and moderate exercise can help relieve its symptoms.

Skin irritation may result from external radiation. Taking care of the affected area, protecting it from the sun, and using creams your doctor prescribes help your skin heal.

Nausea and diarrhea may be a problem if you’re receiving radiation in the abdominal or pelvic area. You may be able to control some of these side effects by adjusting what and when you eat.

Choosing a treatment center

If you’re having radiation therapy, you’ll want to find the best facility for the type of treatment you need. Usually your choices are a comprehensive cancer center or hospital, or an independent clinic. The chief considerations are the sophistication of the radiation equipment, the depth of experience of the radiation team, and access to other treatments, including complementary therapies.

State-of-the-art equipment and an experienced team provide more accurate radiation therapy. Many, but not all, facilities keep track of new advances and keep their technology current. A few provide integrated services across health and wellness disciplines.

You may want to consider traveling away from home to receive the most appropriate treatment for your situation. Some facilities provide reasonably priced accommodations for people who are undergoing treatment and their caregivers and families.