Even if you're buying time with every trial, all you've done is turn the patient into a lab rat for physicians to play around with. The ideal patient needs to be dead enough to have no human rights, but alive enough to participate in the trial. The hope of a miracle cure means the patient doesn't believe himself to be dead enough to not have human rights anymore. It's a paradox.
Signing the documents for such a trial is equivalent to signing your consent for euthanasia. It shifts the blame of death from the cancer to the company performing the trial. It's an extended form of organ donations where you donate your entire body while you're still alive.