Ha! I thought of a few more..
1. When people lower their voice and ask sympathically, "How are you?" Respond with, "You wouldn't believe how having the Clap burns!! I really dred going to the bathroom. OH!!! Wait! You meant THE CANCER?!?"
2. You can also cough delicately into your hand a la consumption. "It's THE CANCER. Ha! Kidding!!"
3. When people ask if you are bothered by the fact that having chemo might reduce your ability to have children, respond with, "But that's the great thing about being bald, frail-looking, and at the hospital all the time. No one would ever suspect you are planning to swipe a few babies from the Maternity Ward. I can scope out the ones that look good."
I'm looking for some more evil (pronounced E-Vile) suggestions to have fun when you have breast cancer. Just submit them via "Comment."