If you can identify a trial that might suit you, you can apply to be in it. Every trial has its own rules about who can participate, called the
inclusion/exclusion criteria, based on age, disease condition, previous treatments used, and other factors. Your own doctor doesn't have to be affiliated with the study but you usually have to be at one of the facilities running the trial. Many trials are held at the National Institutes of Health in Bethesda, MD.
The best source of clinical trial information is
clinicaltrials.gov.