RADIATION DOSE

# Field Size and Dose

Radiation Dose and field size:

Tumor size | Margin | Doses |
---|---|---|

< 2 cm | 1.0 to 1.5 cm margin | 64 Gy in 32 fractions 55 Gy in 20 fractions 50 Gy in 15 fractions 35 Gy in 5 fractions |

> 2 cm | 1.5 to 2.0 cm margin | 66 Gy in 33 fractions 55 Gy 20 fractions |

# Post surgical RT

- to 50 Gy in 20 fraction or
- to 60 Gy in 30 fraction.

# Poor Performance status

- 32 Gy in 4 fractions
- 20 in 1 fraction for small lesions.

# Electron beam vs Orthovoltage

- wider field margin is needed than with orthovoltage due to wider penumbra
- dose specified at 90% of the Dmax to account for the relative biologic difference between the two modalities.
- orthovoltage dose is specified at Dmax (skin) to account for the relative biologic difference between the two modalities.

page revision: 2, last edited: 22 Jun 2008 20:13