Cancer clinical trials, also called research studies, test many types of treatments such as new drugs, new surgical techniques or radiation therapy, new combinations of treatments, or new methods. The goal of the research is to find better ways to treat cancer. Cancer clinical trials include research at four different phases. Each phase answers different questions about the new treatments.

What Happens in Cancer Clinical Trials?

In clinical trials, patients receive treatment and doctors carry out research on how the treatment affects patients. A person’s progress is closely monitored during the trial. Once the treatment portion of the trial has been completed, patients may continue to be followed in order to gather information regarding specific endpoints. These endpoints are defined prior to the study being started and may include time for disease progression and/or overall survival.

While clinical trials have risks for the people who take part, each study also takes steps to protect patients.

Informed Consent

Informed consent is an ongoing process during a cancer clinical trial in which all of the available information about the specific trial is discussed with the person participating in the trial. The doctor or nurse reviews the treatment plan, including potential risks and benefits of the treatment with the participant. This information is also written in a document (consent form) which is presented to the participant before treatments can begin. After the potential study participant reads the document, an opportunity to ask questions about any parts of the form that are unclear is given. If the person agrees to participate in the study, the consent form is signed. Signing the form indicates that the study participant read the form and the doctor or study nurse answered any questions about the information contained in the form, which may have been unclear. Signing a consent form does not mean a person must stay in the study. In fact, a person may leave the study at any time. If a person chooses to leave the study, a chance to discuss other treatments and care with their doctor is given, and their care will not be affected in any way.


The protocol is the action plan for a clinical trial. The plan states what will be done in the study and why. It outlines how many people will take part in the study, what types of patients may take part, what tests they will receive and how often, as well as the treatment plan. Each doctor that treats patients in the study uses the same protocol, and must follow the guidelines that are specified. The federal Food and Drug Administration (FDA) has general guidelines that must be followed by any physician or institution conducting clinical trials. Before the FDA can approve a treatment, the study results are audited to ensure the trial was conducted safely and according to these guidelines.

For patient safety, each protocol must also be approved by the organization that sponsors the study. The Scientific Review Committee, a group of individuals from the institution, including physicians, scientists, nurses, administrators, review the protocol for scientific merit and feasibility of the protocol. The Institutional Review Board (IRB) of the hospital must also approve it. This board includes consumers, clergy, and health professionals. They review the protocol to try to be sure that the research will not expose patients to extreme or unethical risks.

Eligibility Criteria

Eligibility criteria are guidelines from the protocol, which describe the characteristics that all participants in the study must have. These criteria differ from study to study, depending on the purpose of the research. Examples are: age, gender, the type and stage of cancer; and whether cancer patients who have had prior cancer treatment or have other health problems can participate.

Phases of Clinical Trials

Phases of Clinical Trials

Cancer clinical trials include research at four different phases. Each phase answers different questions about the new treatments.

Phase I Clinical Trials

Phase I cancer clinical trials are the first step in testing a new cancer treatment in humans. The questions being explored in Phase I trials are: what is the best way to give a new treatment; can this medication be given safely to humans; and what is a safe dose? These cancer clinical trials have a limited number of patients who would not be helped by other known treatments.

Phase II Clinical Trials

Phase II cancer clinical trials focus on learning whether the new cancer treatments have an anti-cancer effect on a specific type of cancer. Additional information regarding the side effects of the cancer treatments is also obtained. A small number of people are included because of the risks and unknowns involved.

Phase III Clinical Trials

Phase III cancer clinical trials compare the results of people taking a new cancer treatment with the results of people taking a standard treatment. Some of the questions being asked in a phase III cancer clinical trial are: which group has better survival rates or fewer side effects?

Persons in the cancer clinical trial are assigned at random (a process similar to flipping a coin) to either the new treatments (treatment group) or the current standard treatment (control group). Randomization helps to avoid bias (having the study’s results affected by human choices or other factors not related to the treatments being tested) in a cancer clinical trial. When no standard treatment exists for a cancer, some studies compare a new treatment with a placebo (a look-alike pill/infusion that contains no active drug). However, a person is told if this is a possibility before deciding whether or not to take part in a cancer clinical trial.

Comparing similar groups of people taking different treatments for the same type of cancer is another way to make sure that the cancer clinical trial’s study results are real and caused by the treatment rather than by chance or other factors. These trials may include hundreds of people from different centers around the country.

Phase IV Clinical Trials

Phase IV cancer clinical trials, also called post-marketing studies, are trials conducted after a treatment has been approved. The purpose of these trials is to provide an opportunity to learn more details about the treatments, such as: the mechanism of action; fine points regarding toxicity; quality of life; and questions that may have come up during other phases of trials. These "post-marketing" cancer clinical trials can be conducted in a phase I, II or III format.

Benefits & Drawbacks of Participating

Benefits & Drawbacks of Participating

Possible Benefits of Cancer Clinical Trials

  • Clinical trials offer high-quality cancer care.
  • You may be among the first to benefit from a new treatment.
  • By looking at the pros and cons of clinical trials and other cancer treatment choices, you are taking an active role in a decision that affects your life.
  • You have the chance to help others and improve cancer treatment.

Possible Drawbacks of Clinical Trials

  • New treatments being studied are not always better than, or even as good as, standard care. They may have side effects that are unexpected or that are worse than those of standard care.
  • Even if a new cancer treatment has benefits, it may not work in your case. Even standard treatments, proven effective for many people, do not help everyone.
  • If you receive the standard treatment rather than the new treatment being tested, it may not be as effective as the new approach.
  • Insurance companies do not always cover all patient care costs in a study. What is covered varies by plan and by study.
Important Questions to Ask

Important Questions to Ask

Questions You Should Ask the Doctor

  • What is the purpose of the study?
  • What has previous research of this treatment shown?
  • What is likely to happen in my case with or without the treatment?
  • Are there standard treatments for my type of cancer?
  • How does this study compare with standard treatment options?

Questions You Should Ask the Doctor or Study Nurse

  • What Phase is this cancer clinical trial?
  • What are the possible short- and long-term risks, side effects and benefits of the treatment?
  • What kinds of treatments, medical tests, or procedures will I have during the study? And how do they compare with what I would receive outside of the study?
  • How long will the study last? Will there be a follow-up after the study?
  • Where will my cancer treatment take place? Will I have to be in the hospital?
  • How will I know the treatment is working?
  • How could the study affect my daily life?
  • Will my records be kept confidential?
  • Will the study cost me anything?
  • If I decide to withdraw from the study, will my care be affected? Will I need to change doctors?