Who decides which group I am in?

Chance does. Like a coin toss. Not me, and not you. I know that sounds wrong.

If I picked, I would send the patients I feel most hopeful about to the new drug. I would not mean to. Then the new drug would look good and we would have learned nothing. You still choose whether to join at all.

Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.