Using a single dose of 800 cGy delivered to a tumor produces what effect compared to 4 fractions of 200 cGy each?

Administering a single dose of 800 cGy to a tumor typically results in more biological damage when compared to dividing this dose into four fractions of 200 cGy each. This phenomenon can be attributed to the principles of radiation biology and how the body reacts to radiation dosing.

When a higher dose of radiation is delivered at once, it can exceed the threshold for cellular recovery mechanisms. Tumor cells are often less capable of repairing damage from large doses of radiation, which can lead to increased cell death. On the other hand, fractionating the radiation dose into smaller parts allows healthy tissues to recover between treatments, thereby reducing collateral damage and limiting potential side effects.

Additionally, tumor cells may be more responsive to repeated lower doses due to effects such as repopulation and reoxygenation, which can enhance the effectiveness of therapy over time. Hence, when considering biological effects, a single high dose is generally more damaging to the biological tissues affected than multiple lower doses.