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How a Clinical Trial Works

Clinical trials are conducted worldwide under rigorous guidelines to help doctors find out whether new cancer treatments are safe and effective or better than the standard treatment.

Before a trial begins, a new therapy is often developed and tested in a laboratory. It's then thoroughly tested in animals. If this early research (the preclinical testing) shows promise that the therapy may be safe and effective, a carefully planned and monitored clinical trial of the drug or treatment will be conducted in people.

Doctors who specialize in cancer research develop and lead cancer clinical trials. They determine the study's protocol (procedures and design), including:

  • The disease to be treated
  • The treatment to be tested
  • The study goal(s) (sometimes called endpoints)
  • The type of patient who will be an appropriate participant
  • The methods to be used to protect the participants' safety
  • How much medicine or other treatment will be given to patients
  • How long the treatment will be studied

A trial can take place at a few specific locations or be conducted from many venues across the United States. In many cases, participants can be treated at various locations, which may include a large cancer center, a university hospital, a clinic, a local medical center or the doctor's office.


Clinical Trial Phases

A cancer clinical trial is divided into four parts, called phases, each with a specific purpose. As each phase is successfully completed, the trial moves into the next phase.

Phase I

Treatment is tested in a very small group of patients to determine:

  • Its safety
  • The appropriate dose (amount)
  • The best way to administer the treatment

Researchers watch patients closely for possible side effects.

Phase II

Treatment is tested in a larger group of patients to determine:

  • Whether the treatment works
  • How well the treatment works

Researchers continue to monitor patient safety in phase II and throughout the trial.

Phase II studies with positive results will move into phase III.

Phase III

Phase III trials are "randomized." This means a "treatment group" is compared to a "control group." In a randomized trial:

  • The treatment group is made up of large numbers of patients who receive the study treatment
  • The control group is made up of large numbers of patients being treated with the best standard treatment
  • The treatment outcomes for the two groups are compared at specific time intervals

The U.S. Food and Drug Administration approves a treatment if it passes phase III testing. The treatment must meet safety requirements and either be more effective than standard treatment or equally as effective as standard treatment but with less toxic side effects.

Phase IV

By the time a clinical trial enters phase IV, the FDA has already approved the treatment. Phase IV studies are often performed to:

  • Identify an additional use for an already approved drug or other treatment
  • Gather additional information on safety and effectiveness from a larger group of patients
  • Establish effectiveness in a subgroup of patients — for example, patients over age 65

Differences Between Clinical Trials and Standard Treatment

  • Patients' responses to treatment are followed closely in a study. Patients may receive more tests during treatment and have more doctors' visits as part of the clinical trial than they would in a standard care setting.
  • Treatment routinely covered by health insurance or managed care plans may no longer be covered for patients enrolled in clinical trials. In some plans, coverage for patients receiving treatment as part of a clinical trial is set up differently. See Clinical Trial Insurance Issues.
  • Patients may not know whether they're receiving the study treatment or the best standard treatment. Many cancer clinical trials compare two patient groups. However, federal regulations require that patients be told if a placebo (a substance that looks the same as the treatment but is inactive) will be used in a trial. Placebos are not typically used with patients in cancer clinical trials.