Dose Enhancement Factor

The dose enhancement factor is similar to other radiobiological ratios (such as oxygen effect, relative biological effectiveness). In this case, it refers to:

\begin{align} \text{DEF}=\frac{\text{Dose with Radiation Alone}}{\text{Dose with Radiation + Drug}} \text{for the same biological effect} \end{align}

If the DEF is greater than one, then the addition of the drug is functioning as a radiosensitiser. If the DEF is less than one, then the drug is a radioprotector.