This week's artwork was donated by Dathan, a pediatric cancer patient who received treatment at The Children's Hospital of Philadelphia .
Clinical trials are research studies conducted with people.
Cancer prevention trials study ways of reducing the risk, or chance, of developing certain types of cancer. Prevention trials are conducted with healthy people who have not previously had cancer. There are two kinds of cancer prevention clinical trials. Prevention clinical trials are conducted in phases. Phase II trials focus on learning whether the agent has an effect in preventing cancer.