DONT DO IT !!! Today, many people with cancer find this type of action very offensive. There are some exceptions such as fund raisers etc, and most of these are done for children's cancer treatment and research.
Most adults I know, including myself that had cancer find this very rude and offensive and think more of it as an individual trying to gain attention to themselves, not cancer..
If you want to cut your hair, that's fine, you can donate it it to such charities as "Locks of Love". Many of the people that accept hair for this situation have many rules as to the type of hair,, length etc so look it up before you do it. You dont have to SHAVE your head for this.
Also, the wearing of wigs, at least where I live is falling out of favor for adult cancer patients. They have so many trendy head accessories for woman, and men now-a-days this is the trend.
Not one woman in my Cancer/Infusion Center wore a wig. They wore really neat scarves, hats, beanies, Knitted hats. I would wear a beanie or a baseball cap.
So my advice, dont do it....