People are asked to take or do something.
In some studies, people are asked to do something
to lower cancer risk. For example:
- Exercise
- Follow a special diet.
In most studies, people are asked to take something
to lower cancer risk. For example:
- Take a medicine
- Take a vitamin.
When people are asked to take something,
it may be:
- The standard agent: A medicine or vitamin that is
already used to prevent a certain cancer
- The study agent: A new medicine or vitamin that
doctors hope will be better than what is already used to
prevent a certain cancer
- The placebo: A pill that has no medicine at all. It helps
doctors figure out whether or not the study agent really
works to prevent cancer.
![](https://webarchive.library.unt.edu/eot2008/20080917235138im_/http://www.cancer.gov/images/Documents/77c74af0-5263-48ef-86dd-acf991198393/CTES_PrevBrochEnglishAPP104.jpg)
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