What should you know about EQD2 radiotherapy?

The same total dose can have a different biological effect when divided into different fraction sizes. EQD2 combines total dose, dose per fraction and a tissue-specific radiobiological assumption to create a common comparison. It can be considered for the tumour and for nearby normal tissues.

This is a planning estimate rather than a dose delivered by a machine. It does not by itself predict how an individual will respond. The radiotherapy team also considers the treatment area, timing, previous treatment, imaging and your general health.

If EQD2 appears in your notes, ask which area it describes and whether it includes an earlier course of radiotherapy. Request the total dose, dose per fraction and number of treatment visits in plain language so you can understand the comparison.

Do not change or skip treatment based on an EQD2 number. Your team may use the calculation when selecting or reviewing schedules for skin, breast, brain, bowel, cervical or head and neck cancers.

During treatment, contact the radiotherapy service promptly for severe or rapidly worsening pain, marked skin breakdown, repeated vomiting, new confusion or weakness, breathing difficulty, or inability to drink. These symptoms need clinical assessment regardless of the EQD2 value.

What does my EQD2 number represent? Which tissue model was used? Does earlier radiotherapy affect the calculation? What does this mean for the dose to nearby healthy tissue?