Clinical trials

A clinical trial is the term used to describe a research study. Research into new ways of preventing, screening and treating cancer goes on all the time. This factsheet discusses clinical trials into cancer treatments.

Clinical trials look at using new drugs or combinations of currently used drugs to treat cancer. Clinical trials also look at diagnostic techniques, surgical techniques and radiotherapy treatments. The aim of clinical trials is to improve treatments for cancer, and give patients with cancer a better quality of life.

Many cancer patients take part in clinical trials. Even though the words ´research´ and ´trial´ sometimes scare people, there is no need for fear. Before a drug or treatment is used on patients, it goes through many steps to make sure it is safe to use.

If the early stages of research suggest that a new treatment might be more effective than the current or ´standard´ treatment, doctors and researchers compare the new treatment with the standard treatment.

A clinical trial is one of the final stages of this long and careful research process.

If you are interested in taking part in a clinical trial, speak to your doctor. They are in the best position to advise you about any trials that may be suitable for you and your cancer.

Why are clinical trials needed?

The idea for a cancer trial usually comes from looking at current research. Based on what they already know, researchers identify gaps and find new questions that need to be answered. The researchers then set about ‘designing’ the trial, this is known as a trial protocol.

The treatments we currently use for cancer have been tested in clinical trials. Without ongoing clinical trials it would not be possible to develop new and more effective treatments. Once a clinical trial has shown that a treatment is effective, further trials are often carried out to find better ways of using it, for example using different doses or combining it with other treatments.

Cancer trials often require thousands of patients and can take a number of years to complete. This is because the researchers want to be sure that a new treatment or new way of giving an existing treatment is better than the standard treatment.

Sometimes, despite the large numbers of patients involved and years required, the improvements in treatment are important but small. However some trials do result in significant changes to cancer treatments. This is why it is so important that researchers continue to design new trials and patients agree to take part.

Trial safety and regulation

In Ireland, all medicines must successfully complete a clinical trial before they are granted a license. Researchers must register with and submit their trial protocol along with relevant scientific and medical information to the Health Products Regulatory Authority (HPRA). The HPRA reviews their application and decides whether or not the trial can be conducted.

The application must also be sent to an approved ethics committee, for new medicines this process is supervised by the Department of Health and Children. The ethics committee ensures that the rights and well being of the patients who are taking part in the trial are preserved.

Once the trial application has been passed by the HPRA and the ethics committee, the researchers can begin the trial. At any time the HPRA can audit the trial to ensure it is being carried out properly with the patients´ safety in mind.

What are the different types of clinical trials?

Some of the main terms used to describe different types of trials are explained below. Your doctor or nurse will explain which of these terms are relevant to you.

Controlled trials

Some trials require a trial group of patients and a control group of patients. The trial group receives the new treatment and the control group receives the standard treatment. This allows the researchers to compare the two treatments. If you take part in a trial and are assigned to a control group, your participation is just as important to the results as the patients in the trial group.

Blind and Double-blind trials

Sometimes it is necessary for your doctor to not tell you what treatment you are getting. Therefore you will not know if you are receiving the new treatment or the standard treatment. The reason for this is that the researchers need to know that the reported results are not influenced by what the medical team or patients think might or should happen. By the medical team not knowing what treatment you are getting, they will be able to give a report that will not be influenced in any way.

Don´t worry, if necessary it is always possible to find out from the researchers organising the trial what treatment each patient is receiving.


Randomisation is a term used to describe how patients are selected into groups. Those receiving the new treatment(s) and those receiving the standard treatment(s). A computer randomly selects patients into the two groups. This is to ensure there is no bias.

Randomisation ensures that the trial is fair and that the results are reliable. This is important considering the results may influence treatment for patients in the future.


Many patients worry that if they take part in a trial they will be given a placebo. A placebo can look like a real drug but it has no effect on the body. Placebos are used when there is no standard treatment to compare the new treatment to.

However placebos are rarely used in cancer clinical trials. If a trial uses placebos you will be informed before you decide to take part.

What does a trial “phase” mean?

As already mentioned, clinical trials are long and careful research processes that take many years. There are several “phases” in a clinical trial. A new treatment must pass each phase in order to move on to the next phase. These phases ensure that the research is carried out in an orderly way and that patient safety is maintained at all times. Remember if you chose to take part in a clinical trial it will be most likely a phase 3 or 4 clinical trial.

Phase I (Phase 1)

Phase 1 is the first stage that a new treatment is used on people. Prior to this the trial is carried out on cancer cells in a test tube or petri dish in a laboratory. Phase 1 trials involve small numbers of people, usually less than fifty and as few as ten. The purpose of a phase 1 trial is;

  • To find a safe dose for the new treatment
  • To decide how the new treatment should be given (eg. Tablets / intravenous)
  • To see how the new treatment affects the human body

Phase II (Phase 2)

A phase 2 trial also involves a small number of patients, usually less than one hundred. The purpose of a phase 2 trial is;

  • To determine if the new treatment is particularly useful to certain cancers
  • To see how the new treatment affects the human body and what the side effects are
  • To see if the new treatment is suitable for a phase 3 trial.

Phase III (Phase 3)

Phase 3 trials involve much larger numbers of patients often across many different hospitals in many different countries. A phase 3 trial may require anything from one hundred patients to thousands of patients. The purpose of a phase 3 trial is;

  • To compare the new treatment with the standard treatment
  • Provide more information on the side effects of the treatment

Phase IV (Phase 4)

If a phase 3 trial proves a new treatment is effective, the treatment is licensed and doctors will begin using it routinely on their patients. Phase 4 trials further assess the effectiveness of the treatment and the associated side effects. Phase 4 trials require thousands of patients.

How long does a clinical trial take?

Clinical trials can take many years to complete. Even though your treatment as part of the trial is compete, all final results of the whole trial may not be known. This can be frustrating for patients, doctors and researchers. However it is necessary that a trial be run for long enough to recruit enough patients and then have the results analyzed to ensure the results are reliable. Your doctor will discuss the details of your treatment with you, including how long it will take.

Once you have completed your treatment, you will be monitored by your doctor and they will continue to report back to the researchers. Remember trials can require hundreds or thousands of patients and each patient starts their treatment at a different time and must be monitored during and after their treatment.

Results are published in medical journals. Your consultant will be able to tell you what the final results are once they have been published. If a trial treatment is proven to produce better results than the standard treatment it will be licensed and become the new standard treatment.

Considering a clinical trial

If there is a clinical trial that is suitable for you, your doctor will explain this and your treatment options. For example you may be offered the standard treatment for your cancer and you may also be offered a trial treatment. Remember you will only be offered a trial treatment if your doctor thinks it is at least as good as if not better than the standard treatment.

Trials must be very specific so they require patients to be as similar as possible. For example a new treatment may be designed for a rare type of lung cancer and would therefore not be suitable for all lung cancer patients. For this reason trials have very strict inclusion and exclusion criteria.

This means that some people can be included in the trial but some are excluded. Not everyone is suitable for a particular trial. The inclusion and exclusion criteria refer to reasons why you may or may not be suitable.

Age, gender, cancer type, stage of cancer, whether you have had previous cancer treatment and other medical conditions are all types of inclusion and exclusion criteria. Strict patient selection criteria help to make the trial safer by ensuring that the right ‘type ’ of patients are receiving the new treatment and that a fair comparison can be made between similar patients.

Your doctor will go through the trial details with you, you will then have an opportunity to think about your choice and discuss your options with the trial nurse. If you decide to take part in the trial, your doctor and nurse will monitor you very closely.

Before you commence the trial treatment you will be asked to read a detailed patient information sheet and sign a consent form. This can involve a lot of paperwork but don’t worry your doctor and nurse will go through this with you. The consent explains why the trial is being run, what it hopes to achieve, what the possible side effects are and why you have been invited to take part. It is important that you understand the trial before you agree to take part, this is called informed consent.

Remember taking part in a trial is your choice, so take your time and ask your doctor any questions that you might have. Be assured that trials are confidential and your personal details will be protected.

You can withdraw from the clinical trial at any time and this will not affect the care you receive from your doctors and nurses. If you decide to withdraw, you will be offered the standard treatment instead.

Weighing the advantages and disadvantages of taking part in a clinical trial

Deciding what treatment to have can be confusing. Remember you will only be given a choice if your doctor believes that both treatments could be of equal benefit to you. There are pros and cons to taking part in a trial, some of the main ones are listed below. If you have any questions about these, discuss them with your doctor:


  • You have an opportunity to have a promising new treatment
  • If the trial treatment is proven to be better than the standard treatment, you will be one of the first patients to receive it
  • You will be closely monitored by a team of doctors and trial nurses
  • You may be helping improve cancer treatment for future patients


  • The trial treatment may be as good but not better than the standard treatment
  • There may be unexpected side effects with the trial treatment
  • You may be required to make more visits to the hospital than patients who are on standard treatment
  • Health insurance companies may not cover costs associated with a trial so it is important to contact your health insurance company before you commence the trial

Regardless of what treatment you decide to have, remember every patient is different and there is no way of knowing if a treatment is going to work for you before you commence it. Your doctors can only advise you based on what they have learnt from other patients with similar disease so make your decision based on what you feel is best for you.

Questions to ask your doctor

It is a good idea to bring somebody with you when you are meeting your doctor to discuss a clinical trial. Remember the information can be confusing so don´t worry about asking questions. Perhaps write your questions out before you go to your appointment.

If you are between check-ups and have a symptom or problem that worries you, let your doctor know right away.


  • What is the purpose of the trial?
  • What is the trial called?
  • What treatment will I be receiving?
  • What is the difference between the trial treatment and standard treatment?
  • What are the side effects of the trial treatment?
  • What are the benefits of taking part in the trial?
  • What are the risks of taking part in the trial?
  • How many patients are taking part in this trial?
  • How long will my treatment take?
  • Will the trial cost me money?
  • Will I be in the same hospital and have the same doctors?
  • What treatment will I have if I do not want to take part in the trial?
  • What will happen if I want to discontinue the trial treatment?
  • When will the trial results be available?

Our Journey Journal is a place to record the important information that you receive during your hospital visits. You can keep note of appointment times, test results, cancer care team contact details, treatment details and support services information.

If you are in a clinical trial, you may find our journey journal useful. You can download it here or call our Cancer Nurseline for a free copy on Freefone 1800 200 700. 

Further information

For more information about clinical trials or about cancer in general, call the Cancer Nurseline on Freefone 1800 200 700 (Monday–Friday, 10am–4pm) or email for confidential advice from our cancer nurse specialists.

For more information on clinical trials, see our  factsheet on Cancer and Clinical trials.

Clinical trials in Ireland

You can ask your doctor or nurse in your hospital and they will let you know about the availability of clinical trials. You can also find out what trials are available in Ireland by contacting Cancer Trials Ireland who co-ordinate cancer clinical trials. Cancer Trials Ireland has produced a short video on clinical trials in Ireland. 
Sometimes clinical trials are run involving the hospital consultant and a pharmaceutical company directly. Ask your doctor about this. 

Useful organisations and websites:

Note: Links to external websites listed on this page. The Irish Cancer Society is not responsible for the contents of external websites.

Irish information

Cancer Trials Ireland
The organisation that brings cancer clinical research to Ireland
Tel: 01 6677211 / Email

Health Research Board
Tel: 01 234 5000
Fax: 01 661 2335 / Email

Health Products Regulatory Authority 
Tel: 01 676 4971 / Email

The Irish Platform for Patient Organisations, Science and Industry (IPPOSI)
Clinical trial information, including information specifically for children.

Department of Health
Website: Department of Health

Website: Health Service Executive

International information:

Website: International Federation of Pharmaceutical Manufacturers Association

Website: National Cancer Institute clinical trials

EU Clinical Trials Register
Website: EU Clinical Trials Register

Date Last Revised: 
Monday, May 15, 2017