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Components of a clinical trial

Each clinical trial has its own protocol (action plan), criteria for eligibility and informed consent. It is important to understand what these are before deciding to enrol in a trial.

Trial protocol

A protocol is a written description of the trial. It explains why the trial is being done, how it will be conducted and how the person’s safety will be protected.

The protocol outlines:

  • why the trial is being done and the background evidence to support the trial
  • who can participate in the trial (eligibility)
  • how many people will take part in the trial
  • what medical tests participants will have and how often
    • Information gathering for the study may include forms that need to be filled out by the participants and a number of tests, such as blood tests, x-rays and other imaging tests.
    • Participants’ progress will be followed closely, often requiring a few extra visits to the health centre.
  • how long the trial is expected to last
  • what type of treatment will be given and how often
  • what side effects participants might experience during the trial
  • how the researchers will determine if a treatment is effective (endpoints)
  • if follow-up visits are requested and how often

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Eligibility criteria

Clinical trials often enrol people who share many of the same characteristics. This is to make sure that the trial results will be scientifically accurate and are not thrown off by personal characteristics. The rules about who is eligible, known as eligibility criteria, are used to decide if a person is suitable for a particular clinical trial. Eligibility criteria may differ from one phase of a study to another.

The eligibility criteria may include:

  • age and sex
  • the type of cancer
  • the stage of the cancer
    • The stage includes whether or not the cancer has spread to other parts of the body, and where it has spread (brain, liver, etc.).
  • the results of certain lab tests
  • a person’s overall health and whether they are being treated for other medical problems
  • whether a person has had any previous cancer treatment
  • how many and what types of cancer treatments a person may have received
  • the length of time since the person last received treatment
  • how close a person lives to the cancer centre or hospital where the treatment will be given

These criteria also help researchers understand who will benefit most from a new treatment. For example, a new treatment may work for one cancer but not another, or it may be more effective at certain stages of cancer.

People who do not have the opportunity to or are not eligible to participate in a clinical trial may apply to receive an experimental treatment through Health Canada’s Special Access Programme.

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Informed consent

Ethical standards apply to clinical trials. People considering a clinical trial should be given all the facts about a clinical trial before they decide to take part. This important process is known as informed consent. People interested in taking part in the study receive a printed consent form that outlines key facts about the study. These include:

  • details about the treatments
  • tests
  • any potential benefits, risks or side effects
  • the contact person for the study should they have questions at any time

If people agree to take part, they will be asked to sign the informed consent form. A person who has signed the informed consent form may withdraw from participating in a clinical trial at any time.

Parents or caregivers will be asked to give permission for their child to participate in a clinical trial. This is called giving parental permission, which is a type of informed consent. Parents will be asked to sign a form that describes the plan.

If children are old enough to understand the treatment plan, they will be asked to agree with the plan as well. When a minor (a child less than 18 years of age) agrees with the plan, the child is giving assent. The healthcare team will help explain the treatment plan to children in words they can understand.

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An endpoint is a measurable component of a clinical trial that helps the researchers to determine the effectiveness of the trial.

Treatment trial endpoints often include tumour response (if and how well a treatment worked as measured by tumour shrinkage or the time it took for a tumour to start growing). Endpoints also include participant survival. Disease-free survival and overall survival are 2 specific measures of survival.

  • Disease-free survival is the amount of time a participant survives without the cancer coming back (recurring).
  • Overall survival is the amount of time a participant lives.

A supportive care trial endpoint may determine how well a person’s symptoms were controlled.

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Study groups and trial status

In phase I and II clinical trials, researchers are trying to determine how to give experimental treatments safely and their effect in people with cancer. People in these studies usually receive the same treatment, although the dose, schedule or both may differ between participants.

In phase III studies, researchers are trying to compare new treatments with those that already exist, so there are usually 2 or more study groups or arms. Studies may be single armed, double armed or have multiple arms. Studies may also be planned (not yet open to participants), open (accepting participants) or closed (no more participants are needed).

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In most cancer treatment trials in Canada, the provincial health insurance plan or the group sponsoring the study will cover the cost of care, medicine and testing. Taking part in a study may result in some costs or expenses for the person participating. These might include the cost of getting to the treatment centre or medicine to treat side effects of treatment, such as anti-nausea drugs. It’s a good idea to ask the healthcare team about possible additional costs. These extra costs are covered in some clinical trials.

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Finding out the results

After a clinical trial, researchers look carefully at all the results before making any conclusions about the study’s medical importance. The results of clinical trials are often published in scientific journals. A really important finding may also be reported in the media.

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Withdrawing from or stopping a study

Taking part in a clinical trial is voluntary. People may leave the trial at any time. If they choose to leave the trial, they will continue to receive the best standard treatment. A person may withdraw from the study at their request, or sometimes in consultation with their study healthcare provider, if it is not in their best interest to continue.

A clinical trial may also be stopped if:

  • it shows that the experimental treatment is not effective
  • serious side effects occur
  • it shows the experimental treatment is more effective than standard treatment
    • In this case, all participants are offered the new treatment.

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Researcher Dr Michael Taylor Dr Michael Taylor is revealing genetic changes in childhood brain cancer.

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