What does an increase in the Oxygen Enhancement Ratio imply?

An increase in the Oxygen Enhancement Ratio (OER) indicates a greater effectiveness of radiation therapy. This ratio reflects how much more effective radiation is in the presence of oxygen compared to its effectiveness in anoxic (oxygen-deprived) conditions.

In biological tissues, the presence of oxygen enhances the damage caused by ionizing radiation. This is primarily because oxygen is a sensitizer for radiation effects, helping to form free radicals that cause additional cellular damage. When the OER is high, it means that when oxygen is available, the radiation therapy is significantly more effective at destroying cancer cells. This principle is crucial in radiation oncology, as it emphasizes the importance of treatment conditions (such as ensuring adequate oxygenation of tumor tissues) to maximize the therapeutic ratio and improve patient outcomes.

The other options do not accurately capture the biological significance of an increased OER.