Clinical Trials: What You Need to Know

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Phase II clinical trials: Does the treatment work?

If a new treatment is found to be reasonably safe in phase I clinical trials, the treatment can then be tested in a phase II clinical trial to see if it works the way researchers think it will.

Usually, a group of 25 to 100 patients with the same type of cancer gets the new treatment in a phase II study. They are treated using the dose and method found to be the safest and most effective in phase I studies. In a typical phase II clinical trial, all the volunteers usually get the same dose, and no placebo is used.

But some phase II studies do randomly assign participants to 1 of 2 treatment groups, much like what’s done in phase III trials (see below). These groups may get different doses or get the treatment in different ways to see which provides the best balance of safety and effectiveness. Phase II studies are often done at major cancer centers, but may also be done in community hospitals or even doctors’ offices.

Doctors look for some evidence that the treatment works. The type of benefit or response they look for depends on the goal of the treatment. This may mean the cancer shrinks or disappears. Or it might mean there’s an extended period of time where the cancer does not get any bigger, or there’s a longer time before the cancer comes back. In some studies the benefit may be an improved quality of life. Many studies look to see if people getting the new treatment live longer than they would have been expected to without the treatment.

If enough patients benefit from the treatment, and the side effects aren’t too bad, the treatment is allowed to go on to a phase III clinical trial. Along with watching for responses, the research team keeps looking for any side effects. Larger numbers of patients get the treatment in phase II studies, so there’s a better chance that less common side effects may be seen. Still, about 70% of phase II cancer drugs don’t advance to phase III, usually because they don’t work well enough.

An example of a phase II clinical trial:

Angela was diagnosed with cancer several months ago. Only one form of treatment, drug C, is known to work for people with her type of cancer, but it only works in about half of the people who get it. After several months of this treatment, Angela’s doctor told her that it did not seem to be helping in her case.

After doing a little research online, Angela and her doctor decide her best bet may be to enroll in a clinical trial. They find a phase II study being done by a doctor nearby, who’s testing a new type of medicine, called “EX-2.” This medicine was already found to be fairly safe in phase I studies. Although not many people have tried EX-2, a couple of people with Angela’s type of cancer were helped by it.

Angela, like all of the other people in this study, will get EX-2 once a week as an outpatient at a local hospital. Before getting the drug each week, she will have a physical exam and blood tests to see how her body is responding to the medicine. She will also have scans done after several weeks to see if the drug is affecting the cancer. She had tests like this while getting drug C, but this time the tests and exams are done more often. All of the extra testing is paid for by the group running the study.


Last Medical Review: 09/21/2012
Last Revised: 09/21/2012