Fractionation and Radiation
What are fractions of radiation?
Radiation therapy is delivered to your cancer in small doses called fractions. Your radiation oncologist will prescribe a total dose which is then divided into smaller doses, or fractions. The amount of radiation you receive is measured in centigray or cGy. A fraction (dose) is given each day and repeated over many days to add up to the total dose of radiation. Radiation is usually given 5 days a week, most often Monday-Friday. This gives your cells 2 days each week to heal themselves.
The fraction and how your radiation is delivered is determined by your Radiation Oncologist. The following can contribute to your Radiation Oncologist’s decision on how to treat your cancer:
- Type of cancer.
- Size and location of your tumor.
- Your general health.
- How well you will be able to stick with treatment.
- Other cancer treatments you are getting.
- The clinical trial you may be participating in.
How are fractions given?
There are different ways to deliver fractions of radiation for your radiation treatment. Some methods are only used in a few cancer types or for certain situations. Your radiation team will choose the best method for your situation. The following are the most common types of fractionation:
- Doses ranging from 180cGy to 200cGy.
- Given once a day, 5 days a week.
- Given over 6-7 weeks.
- This is the most common type of fractionation and is used in many types of cancer.
- Twice a day treatment (6 hours or more apart).
- Smaller doses per fraction.
- Given over the same number of days and weeks as conventional fractionation.
- Examples of cancer treated with hyperfractionation:
- Breast cancer
- Head and neck cancer
- Given over fewer days and weeks than conventional radiation.
- Treatment doses per fraction are higher.
- Treatment is sometimes not given every day.
- Can make the treatment course much shorter. This is not appropriate for all cancer types.
- Examples of cancers treated with hypofractionation:
- Gynecological cancers
- Palliative cancer cases
- Any type of cancer treated with stereotactic radiation therapy (SBRT)
- Given in smaller doses and more than once a day.
- The total dose of radiation is given over a shorter period of time (fewer days).
- Example of cancers treated with accelerated fractionation:
- Head and neck cancers
- Stem cell transplant patients (TBI or total body irradiation)
Palliative Treatment Fractionation
- A treatment used to manage symptoms in cancer that is not curable.
- The 1st to 3rd treatment fractions are delivered at a higher dose to relieve symptoms quickly.
- Between 350cgy-400cGy per fraction for doses 1-3.
- Doses then are reduced to around 200cGy per fraction.
- Palliative treatment fraction can be given for all disease types.
In some cases, shorter treatment courses can be just as effective as longer courses. Discuss with your radiation oncologist which type of treatment fractionation is right for you and your cancer treatment.