If the D0 for an oxygenated tumor is 100 cGy and the OER is 3, what is the D0 of the tumor?

The term D0 refers to the dose required to achieve a specific level of cell death within a given population of cells, specifically in this case, an oxygenated tumor. When considering the oxygen enhancement ratio (OER), which quantifies the increased effectiveness of radiation in the presence of oxygen, the D0 can be adjusted accordingly.

In this scenario, the D0 for an oxygenated tumor is given as 100 cGy, and the OER is stated to be 3. The calculation for the D0 of the tumor takes into account the OER, effectively multiplying the initial D0 by the OER to determine the dose required to achieve the same biological effect in an anoxic (hypoxic) environment.

To find the adjusted D0, you perform the following calculation:

D0 (adjusted) = D0 (initial) × OER = 100 cGy × 3 = 300 cGy.

This means that, for the same level of cell death, the dose required in an oxygen-deficient environment would be three times greater than that required in an oxygen-rich environment, hence the D0 of the tumor effectively becomes 300 cGy. This understanding illustrates how oxygen plays a critical role in the effectiveness of radiation therapy