It's a free will choice. No one can be entered (into a trial) without their informed consent, and that means all known side effects will be listed.

You must believe in free will; there is no choice

We must believe in free will, we have no choice

We have to believe in free-will. We've got no choice.

If you are newly diagnosed with cancer, and there is an effective treatment out there, you can either take it or go into a trial. The choice is entirely yours. It's also important to note if a patient can withdraw from a trial at any time and choose another treatment.

This free will business is a bit terrifying anyway. It's almost pleasanter to obey, and make the most of it.