The experts at the University of Alabama at Birmingham say you are a cancer survivor from the minute you are diagnosed. You aren't dead are you?
Before you go to work, the doctor will stage the disease, recommend a treatment and say what kind of work is appropriate.
Cancer is considered a disability and is governed by many laws. Employers, though, may need to provide time for appointments that exceed the Family Medical Leave Act. They also need to make reasonable accommodations.
One breast cancer survivor who worked throughout recommends:
Take it one bit at a time--one day, one surgery, one treatment.
Cancer may take your hair and your energy, temporarily, but it will give you back new things.
You will manage stress better.
You will discover your coworker support system.
You may even learn to joke about it.
I would add that work is a great distraction--getting out among people, talking, laughing.
Be honest with your supervisor, discuss upcoming events, see if you can work at home if necessary.
Had a bad day? The sun will come up again and you will be there to see it. New start!