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If radiation causes cancer, how can it be used to treat cancer?

Date Published: 02/03/2020 [Source]

Radiation is everywhere. Ultraviolet light streams down from the sun. Radon may seep from the cracks in our basements. Nuclear energy keeps the lights on in millions of homes across the world. X-rays and magnetic resonance imaging (MRI) scans may be used to help diagnose injury and disease. The human body is bombarded with low doses of ionizing and non-ionizing radiation throughout the day, from sources of heat and light to waves from cell phones and microwaves.

In high or sustained doses, radiation may be both damaging and devastating. Radiation may disassemble atoms and cause DNA damage in cells, leading to potentially serious side effects, including cancer. Ultraviolet light from the sun may damage skin cells and increase the risk of melanoma or other types of skin cancer. Radon, an odorless gas found in indoor areas and drinking water, has been linked to an increased risk of lung cancer. High doses of ionizing radiation may damage organs and cause blood diseases or neurologic disorders. So how can something so potentially lethal be used to treat cancer? "We get that question all the time," Bauer says.

Radiation types and effects

There are two different types of radiation: ionizing and non-ionizing. Ionizing radiation is strong enough to remove an electron from the nucleus of an atom. High doses of ionizing radiation may lead to radiation sickness, neurological issues and diseases, including cancer. Sources include ultraviolet light, X-rays, nuclear power or weapons and radon. Non-ionizing radiation is made up of weaker electromagnetic waves that are not powerful enough to disassemble an atom. But this type of radiation may still cause cell damage in high doses. Sources include microwaves, radio waves, TVs, computer monitors and cell phones.

Radiation was first discovered as a potential cancer treatment around the turn of the 20th century. But when radiologists in those early years began developing leukemia, it was soon discovered that radiation may also cause cancer. In the decades that followed, the ravages of radiation poisoning have been recorded in the survivors of the 1945 nuclear bomb explosions in Japan, those exposed to nuclear weapons testing, and victims exposed after the 1986 explosion at the Chernobyl nuclear power plant.

But researchers and doctors have learned to harness the power of radioactivity to damage cells and unleash it on cancer cells. Today's radiation therapy technologies are better able to focus that energy with exacting precision, using tools designed to spare surrounding healthy tissue. The Calypso 4D Localization System, for instance, is designed to adjust the radiation beam to a patient's breathing and other natural movement. TomoTherapy is designed to mold the radiation beam to the exact shape of a tumor. Interventional radiologists have techniques designed to deliver radiation therapy directly to liver tumors. "These technologies reduce the risk of damage to healthy tissue and decrease the chance of a secondary malignancy," Bauer says. "And at the same time, they reduce the potential side effects a patient may experience while undergoing radiation treatment."

Side effects patients experience after radiation treatment may depend on the cancer it is being used to treat. Radiation exposure to healthy lung tissue may cause inflammation and coughing. Damage to healthy tissues in the gastrointestinal tract may cause pain, nausea or diarrhea, Bauer says. And the risk remains that radiation therapy to treat cancers in young people may increase their chance of developing second cancers later in life. "It's definitely something we think about, more so in younger patients," Bauer says. "We don't like to take unnecessary risks if there are other options. But the benefit of the cancer treatment far outweighs the risk of a secondary malignancy. It doesn't mean we ignore the risk."