Defining Clinical Trials

Even before you were diagnosed with breast cancer, you had probably seen a pink ribbon or at least heard of one of the many organizations that fund breast cancer research. Much of medical research concerning cancer begins in a lab with scientists that are making discoveries about cancer cell behavior and potential treatment options based on their behavior. Experiments are conducted to test these new treatments in cell cultures and sometimes animal models. However, research findings in a lab do not always correlate with how a medication or treatment will work in a human. Some degree of non-clinical research must be done and have reliable results prior to beginning trials with human subjects.

Before a new medication or treatment becomes available for use in a large patient population, it is often compared to the standard treatment on a much smaller patient population. Results are carefully recorded and analyzed to determine if the lab findings correlate with clinical findings.

Women who make an effort to understand the purpose of clinical trials and have a good attitude about the need for clinical trials are more likely to participate in them.  Women that participate in clinical trials tend to be younger and are more active in their treatment than those who do not participate in them.1

In these trials, scientists discover:

  • Whether new treatments are more effective than existing treatments
  • If new treatments have acceptable side effects
  • If the risks with the new treatments are less than the potential benefits
  • The dosage required to achieve the most benefit while causing the least harm
  • What patient population will benefit the most from a particular treatment

The goal of a clinical trial is for the FDA (Food and Drug Administration) to give their approval for the drug to begin being used in large patient populations. Many of the treatments that are standard of care today for breast cancer were once part of a clinical trial.

Clinical Trials with Different Goals

Although the tendency is to think that all clinical trials are conducted in an effort to find new treatment for cancer and other diseases, there are many other reasons for clinical trials to take place. Some trials are designed to determine better ways to prevent or detect cancer, while others are investigating new medications or procedures for treatment.

Clinical trials concerning new medications take place in four phases. Each phase of a trial studies an increasing number of patients and adds more information about the experimental drug. If the drug shows no benefit in phase I, then the drug will not continue on into further phases. It is important to realize that clinical trials have inclusion and exclusion criteria. This means that the trial is testing a specific type of patient with a certain type of cancer, at a certain stage and certain patient demographic. Because of these things, they are included in the trial, or able to participate. Others may meet all of those same criteria, but have one factor that excludes them from the trial, such as an unrelated health issue, that keeps them from participating.

Phase I of a clinical trial involves the most risk, as the new medication or treatment has only been tested in the lab and on animals and not on humans. There are typically only 20-80 patients in phase I of a trial, and they are usually patients for whom no other treatment is available or has been successful. During this phase, researchers attempt to calculate a safe dosage range and identify side effects. Some patients participating in a phase I trial will have had some effect in treating their cancer. Phase I is successful if a drug is determined to be safe, no major side effects have occurred, and a safe dosage range has been found. If so, then it is allowed to advance to phase II.

Phase II of a clinical trial involves 100-300 patients and further evaluates effectiveness and safety of the drug. In addition to following treatment response in each patient, researchers are also able to identify additional side effects secondary to an increased patient population. If patients are showing a clinical response to the new treatment and no major side effects have been discovered, then the trial moves on to phase III.

Phase III of a clinical trial involves 1,000-3,000 patients, and further evaluates the safety and side effect profile of the drug. During this phase, the new treatment is compared to standard treatments and efficacy is determined. To do so, there is typically a control group, or group of patients that receive standard treatment instead of the new treatment. In some trials, that may mean a patient gets placebo, or no treatment instead of the new treatment. It is important to understand this when you agree to participate in a clinical trial. Patients are randomized, or randomly assigned to the placebo or treatment group, and both the prescriber and the patient are blinded, also called double-blinded, as to whether or not they have the placebo or treatment. This way, the prescriber cannot be biased toward any individual and since the majority of the data comes from patients themselves, they do not give answers based on whether or not they received the placebo or treatment. All results are honest and unbiased, which gives the most reliable data.

After phase III of a clinical trial, if it has been determined that a new treatment is safe, effective and has tolerable side effects, it is submitted to the FDA for approval. Once the FDA approves it, the new medication or treatment becomes available for widespread use, which is where phase IV trials are performed. These are typically done by drug companies to further delineate the optimal use, risks and benefits associated with the drug.

Very Personal Decision

As with any other part of your breast cancer treatment, you need to stay informed about any treatment options that may be available to you. You need to be prepared to ask your doctors specific questions about trials so that you can feel confident about it if you choose to participate in one.


1 Ellis, Peter M.; Phyllis N Butow; Martin H N Tattersall; Stewart M Dunn; and Nehmat Houssami. (1 August 2001) Randomized Clinical Trials in Oncology: Understanding and Attitudes Predict Willingness to Participate.Journal of Clinical Oncology. v1:15, 3554-3561.

2 Jenkins, v and L Fallowfield. (June 2000) Reasons for accepting or declining to participate in randomize clinical trials for cancer therapy. British Journal of Cancer. v 2:11, 1783-1788.

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.