What effect does the presence of oxygen have on radiosensitivity?

What effect does the presence of oxygen have on radiosensitivity?

• A. It increases radiosensitivity
• B. It decreases radiosensitivity
• C. It can increase or decrease radiosensitivity
• D. It has no effect on radiosensitivity

Answer: (A)

Oxygen increases radiosensitivity because it helps fix the damage radiation causes. When ionizing radiation hits cellular water, it creates free radicals; oxygen reacts with those radicals to form stable DNA lesions that are much harder to repair. This “fixation” of damage makes the radiation more effective at killing cells. In mathematical terms, tissues with oxygen require less dose to achieve the same biological effect than hypoxic tissues, which is why hypoxic (low-oxygen) areas are more radioresistant. Therefore, the presence of oxygen makes cells more susceptible to radiation, so the correct idea is that oxygen increases radiosensitivity.

Oxygen increases radiosensitivity because it helps fix the damage radiation causes. When ionizing radiation hits cellular water, it creates free radicals; oxygen reacts with those radicals to form stable DNA lesions that are much harder to repair. This “fixation” of damage makes the radiation more effective at killing cells. In mathematical terms, tissues with oxygen require less dose to achieve the same biological effect than hypoxic tissues, which is why hypoxic (low-oxygen) areas are more radioresistant. Therefore, the presence of oxygen makes cells more susceptible to radiation, so the correct idea is that oxygen increases radiosensitivity.