Which statement about cellular oxygenation and radiosensitivity is true?

Which statement about cellular oxygenation and radiosensitivity is true?

• A. Higher Oxygenation Decreases Sensitivity to Sparsely Ionizing Radiation.
• B. Oxygenation Has No Effect on Radiosensitivity.
• C. Higher Oxygenation Only Affects High-LET Radiation.
• D. Higher Oxygenation Increases Sensitivity to Sparsely Ionizing Radiation.

Answer: (D)

Oxygen greatly influences how cells respond to low-LET (sparsely ionizing) radiation. When oxygen is plentiful, the free radicals produced by radiation interact with oxygen to form reactive species that “fix” DNA damage, making it permanent and harder for the cell to repair. This increases the likelihood that the cell will die from the radiation. In contrast, in low-oxygen (hypoxic) conditions, many of these radicals are less effective at fixing damage, so more cells survive. This difference is quantified by the oxygen enhancement effect, with oxygenated cells being much more radiosensitive to low-LET radiation. Because of this, higher oxygenation increases sensitivity to sparsely ionizing radiation. The other statements misstate the role of oxygen: oxygen does affect radiosensitivity; the effect is substantial for low-LET but not limited to high-LET radiation; and high-LET radiation is less dependent on oxygen levels.

Oxygen greatly influences how cells respond to low-LET (sparsely ionizing) radiation. When oxygen is plentiful, the free radicals produced by radiation interact with oxygen to form reactive species that “fix” DNA damage, making it permanent and harder for the cell to repair. This increases the likelihood that the cell will die from the radiation. In contrast, in low-oxygen (hypoxic) conditions, many of these radicals are less effective at fixing damage, so more cells survive. This difference is quantified by the oxygen enhancement effect, with oxygenated cells being much more radiosensitive to low-LET radiation.

Because of this, higher oxygenation increases sensitivity to sparsely ionizing radiation. The other statements misstate the role of oxygen: oxygen does affect radiosensitivity; the effect is substantial for low-LET but not limited to high-LET radiation; and high-LET radiation is less dependent on oxygen levels.