How Much Radiation?

The amount of radiation you receive to the breast area depends on factors such as:

• the size of the cancer
• the surgical margins of resection
• the "personality" of the cancer
• whether lymph nodes were involved
• the type of surgery you had

Your doctor will prescribe a total dose of radiation. The total dose is broken up into daily doses, which are also called fractions. The basic unit of radiation is called a rad or centiGray. Generally, you will receive 180–200 rads or centiGrays during each daily session:

• For radiation to the whole breast and/or lymph node areas, the usual total dose is about 4500–5000 centiGrays over 5 weeks. Your doctor may then recommend an additional 1000–2000 centiGrays over 1 week delivered as a boost, targeted to the area where the tumor used to be.
• Partial-breast radiation with external beam or internal radiation usually involves a total dose of 3400 centiGrays given over 1 week.