Questions about Radiation therapy
Short answers, pulled from the story.
What is radiation therapy used to treat?
Radiation therapy is used primarily to kill or control the growth of malignant cancer cells, and it is also applied to non-cancerous conditions such as trigeminal neuralgia, acoustic neuromas, severe thyroid eye disease, and prevention of keloid scar growth. It may be curative when a cancer is localized to one area of the body and has not spread. It is also used as adjuvant therapy after surgery, as palliative treatment for symptom relief, and in combination with chemotherapy, hormone therapy, or immunotherapy.
How does radiation therapy damage cancer cells?
Radiation therapy damages the DNA of cancer cells through direct ionization of DNA atoms and indirect ionization via free radicals, particularly hydroxyl radicals formed when radiation strikes water inside the cell. Double-stranded DNA breaks are especially lethal because they are much harder for cells to repair, and cancer cells have a diminished ability to fix even sub-lethal damage. Accumulated DNA damage causes cancer cells to die or reproduce more slowly.
What are the most common side effects of radiation therapy?
The most commonly reported side effects are fatigue and skin irritation resembling a mild to moderate sunburn. Fatigue typically sets in during the middle of a treatment course and can last for weeks after treatment ends. Depending on the area treated, other effects include dry mouth, dry eyes, nausea, intestinal discomfort, and localized hair loss above doses of 1 gray.
What was the Therac-25 radiation therapy accident?
The Therac-25 was a radiation therapy machine responsible for at least six accidents between 1985 and 1987 in which patients received up to one hundred times the intended radiation dose. Two people were killed directly by the overdoses. The accidents are among the most cited examples of safety failures in medical radiation equipment.
What is fractionation in radiation therapy?
Fractionation is the practice of spreading the total radiation dose across multiple treatment sessions rather than delivering it all at once. The standard adult schedule in North America, Australia, and Europe is 1.8 to 2 gray per day, five days a week. This approach allows normal cells time to recover between doses while tumor cells, which repair damage less efficiently, accumulate harm with each fraction.
How does proton therapy differ from conventional radiation therapy?
Proton therapy uses charged particles that deposit most of their dose at a precise depth in tissue called the Bragg peak, then drop to nearly zero dose beyond that point. Conventional photon radiation continues to deposit energy as it exits the body, damaging healthy tissue in its path. Protons also scatter very little sideways, keeping the beam tightly focused on the tumor's shape and reducing stray dose to surrounding organs.