What Are Clinical Trials for Cancer? Understanding Oncology Clinical Trials

We examine what clinical trials for cancer are, the benefits and risks, and answer other common questions surrounding oncological clinical trials.

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Reviewed by Giselle Leung, PharmD, BCGP

Published 20 March 2024

The importance of cancer clinical trials and studies is crucial when it comes to evaluating the effectiveness of new and experimental cancer treatments for approval and use in hospitals and health centers. For a new cancer treatment to be approved and administered to the general population, it must go through a thorough testing period and then be assessed in a real-world environment with human participants so it is deemed safe.

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Why are clinical trials for cancer important?

Clinical trials are a core component in driving the progress of cancer treatments, allowing researchers to determine if a new drug or treatment offers more advantages when compared to existing cancer treatments. In many cases, clinical trials are the only way for a patient to access new, experimental treatments before they are approved for general use.

Clinical studies are a proven way of helping cancer patients receive high-quality treatment and care that they may not normally have access to. This provides an opportunity to benefit from new therapies and approaches, while also playing a key role in advancing medical research.

Types of cancer clinical trials

Clinical trials that are designed to study cancer treatments come in various forms. Each is tailored to focus on specific research questions, assess varying aspects of cancer treatment and prevention, and deliver unique outcomes.

Below are the main types of cancer clinical trials:

  • Preventive Trials: These clinical trials are designed to discover new treatments that could prevent cancer and its recurrence in individuals. They are aimed at people who have a history of the disease or present a high level of risk. 
  • Screening Trials: Screening trials focus on identifying cancer in individuals early, often assessing individuals who are at risk of cancer but present no apparent symptoms. These trials aim to help medical professionals potentially detect cancer earlier and provide the necessary treatment. 
  • Diagnostic Trials: These trials are aimed at improving and refining cancer diagnosis methods and can involve exploring improved imaging methods, biopsies, blood tests, and other techniques to provide more accurate diagnoses. 
  • Treatment Trials: Treatment trials assess new treatments before they are approved for general use. In terms of cancer, these treatments could include new drugs, combinations of drugs, surgical methods, radiation techniques, immunotherapies, targeted therapies, and other types of treatment. The goal of this clinical trial is to evaluate the safety, efficacy, and potential side effects of experimental treatment. 
  • Adjuvant Trials: Adjuvant trials investigate how treatments can be improved. These trials typically evaluate chemotherapy, radiation, or immunotherapy methods that are given after primary treatments, such as radiation or surgery. The goal of these trials is to find treatments to reduce the likelihood of cancer recurring. 
  • Neoadjuvant Trials: Also known as pre-treatment studies, these trials look at treatments given before the primary treatment. They aim to find methods that make the primary treatments work better, such as attempting to reduce the size of a tumor before surgery or radiation.
  • Palliative Care Trials: These clinical trials are designed to improve the quality of life of individuals who are in the advanced stages of cancer or have metastatic cancer. These studies are vital to finding ways to help patients manage symptoms, improve their comfort, and devise supportive care plans. 

Phases of clinical trials for cancer

Cancer clinical trials are made up of different stages, typically consisting of four key phases. This is carried out in a linear way and each phase is completed consecutively to maintain safety throughout the study. Once a new drug is deemed safe in earlier phases of clinical testing, a clinical trial involving a large group of human participants can then be conducted to determine the optimal dosage.

Each phase of cancer clinical trials plays an important part in discovering new medications or treatments for battling cancer.

Phase 1

When a drug has been approved for human studies, it will be tested on a small number of participants who have different types of cancer or display various genetic changes. The main goal of this phase is to help determine a safe optimal dose of the treatment or drug being studied.

Phase 2

If a drug is deemed safe in Phase 1, it can then progress to the second phase of study which involves a larger number of participants, usually for one or more specific types of and stages of cancer. This phase is designed to determine the optimal dosing of the new drug or treatment and provide an initial assessment of its effectiveness.

Phase 3

The third phase can commence once a new drug or treatment has shown positive outcomes in the previous study phase. In this phase the group of participants increases further, often involving hundreds or even thousands of cancer patients.

Participants will be randomly assigned to groups to receive the new drug or treatment, or an established standard of care, so a comparison can be made. This phase aims to provide definitive evidence of the treatment’s efficacy to support an application for Food & Drug Administration (FDA) approval.

Phase 4

Phase 4 clinical trials take place after approval has been granted by the FDA and are often referred to as post-marketing trials. The aim of phase 4 is to ensure there are no safety concerns or other issues related to the new treatment that may not have arisen during the previous phases.

This phase can often last for a number of years, assessing patient outcomes to determine if there are any long-term side effects for patients or other problems that may affect how the treatment is administered.

What to expect when participating in a cancer clinical trial

If you wish to participate in a cancer clinical trial the most important thing to keep in mind is that the clinical trial process is typically highly structured and stringently monitored.

Before committing to a study, you should fully understand all the details of the trial, including the possible risks, benefits, and potential impact on their cancer treatment. It is advised to discuss the clinical trial with your doctor or healthcare provider to ensure the treatment is fully aligned with your individual circumstances, treatment plan, and overall goal.

Read on to learn what you can generally expect before and during a cancer clinical trial.

Before the trial

Before a clinical trial begins, there are several stages you will need to complete to participate in the study.

  • A Screening and Eligibility Assessment: First, you must undergo a screening process to determine if you meet the eligibility criteria of the trial. This will involve a comprehensive review of your medical history, current health status, the type of cancer you have, as well as what stage the cancer is at. 
  • Informed Consent: Before you can participate in a clinical trial you will receive detailed information regarding the study, such as its intended goals, procedures, potential benefits and risks, and any alternative treatments on offer. 
    During this stage, you will also be given the opportunity to ask any questions and discuss your concerns with a member of the research team. Once these steps are complete, you can then sign an informed consent form.
  • Initial Assessments and Baseline Tests: Once the consent form has been signed, you will undergo a series of baseline assessments and tests. This will include physical examinations, blood tests, imaging tests, and other types of testing to determine your health status.
  • Randomization and Treatment Assignment: Finally, you will be randomly assigned to a specific treatment group. For example, you may be placed in an experimental group that receives the new treatment, while other participants may be in a control group that receives a standard form of treatment or a placebo.

During the trial

A clinical trial is a significant undertaking that involves a lot of monitoring and data collection. To help understand what is involved during a cancer clinical study, we have broken down the process into six main parts.

  • Treatment Administration: Treatment will be assigned based on the trial protocol, while the treatment plan will outline the dosages, frequency, and duration of the treatment. In a cancer clinical trial, this could involve chemotherapy, immunotherapy, targeted therapy, radiation, or a combination of these treatments.
  • Monitoring and Follow-up: There are often numerous follow-up visits throughout the clinical trial. In addition to assessments that monitor a person’s response to treatment, the research team also checks for any side effects and monitors the regression or progression of the cancer. This could include a range of testing, including blood tests, physical examinations, imaging tests, and quality-of-life evaluations. 
  • Adherence to Protocol and Guidelines: The guidelines and protocols of the trial must be adhered to at all times which will be continuously outlined in scheduled appointments with the research team. This may include following a specific diet, taking additional medication, and providing reports regarding any adverse effects.
  • Record Keeping and Data Collection: During the process, the research team will maintain accurate records regarding the treatment of each individual, their responses, and any side effects. This data is vital in terms of assessing the safety and efficacy of the new drug or treatment. 
  • Communication and Support: All participants will be offered continuous support and communication channels throughout the study. The research team will be on hand to provide information, answer queries, and offer support when needed should a person have any concerns. 
  • Potential Changes and Discontinuation: If a person reacts negatively to the new treatment and experiences unwanted side effects, then the treatment could be adjusted, or they could be removed from the trial altogether to protect their safety. 

Benefits of being part of a clinical trial for cancer

There are numerous personal benefits to consider when it comes to participating in a clinical trial, as well as playing a role in advancing cancer treatments for the wider population.

  • Participants might have access to new, innovative treatments that are not yet widely available, including experimental drugs, immunotherapies, and targeted therapies.
  • Clinical studies ensure all participants receive a high level of medical care. This is thanks to the collective expertise and knowledge of leading oncologists, nurses, researchers, and other healthcare professionals.
  • Clinical trials offer close monitoring and care, with frequent check-ups and dedicated medical supervision by specialized healthcare professionals.
  • The potential for positive outcomes is considered high when compared to standard treatments. This is especially the case with experimental therapies that target specific forms of cancer.
  • Many clinical trials cover the cost of experimental treatments and the necessary medical tests, helping to reduce the financial burden of cancer treatment.
  • Clinical trials will often design personalized treatment plans based on the unique characteristics of the patient, including their genetic makeup and response to therapy. This can result in a more effective treatment strategy.
  • Participants are also given ongoing support and are able to connect with other people who are going through a similar experience. This can help to create a sense of community and can help to make cancer treatment a less stressful experience.
  • Anyone taking part in a clinical trial is playing a significant role in progressing medical science and advancing new treatments that can make a huge difference in combating cancer. 

Potential risks of participating in a clinical trial for cancer

Despite the numerous benefits of a clinical trial, you must also understand the risks and uncertainties of a cancer research study.

Some common risks associated with clinical trial participation include:

  • Clinical trials may present unknown risks and side effects due to their experimental nature. This is because treatments and their outcomes are not yet fully understood. These side effects can sometimes range from mild to severe and can affect the health and well-being of individuals in different ways.
  • Treatments being studied may also prove ineffective, with some experimental treatments not delivering the intended outcomes for certain individuals. Like any cancer treatment, there is no guarantee of success.
  • In some trial groups, you may be given a placebo (a substance with no active effects) instead of the experimental treatment. This can be mentally challenging, especially if the person believes they are receiving the active treatment.
  • Cancer clinical trials follow strict schedules and protocols which could result in delays and interruptions to cancer treatment being administered when compared to standard care.
  • Additional tests and procedures may be required when compared to standard care too, potentially placing more physical and emotional demands on participants.
  • Traveling to clinical trial sites to receive treatment and to attend follow-up visits involves certain travel and time commitment, which may prove problematic in terms of logistics and expenses.
  • When participating in a clinical trial you may be restricted from receiving other forms of treatment throughout its duration, limiting alternative options.
  • In some clinical trials, your personal medical information and health records may be shared with third parties or published publicly, presenting confidentiality and privacy issues.
  • You may find participating in a clinical trial emotionally and psychologically challenging, particularly if the treatment proves to be unsuccessful. This emotional strain can be amplified if a person is dealing with a life-threatening condition like cancer.
  • As clinical trials involve new and experimental treatments, the benefits are unproven and there is no guarantee that the treatment will prove more effective than standard care.

How long are cancer clinical trials?

The duration of clinical trials for cancer can vary, in some cases, significantly. This is due to a range of factors which include the trial’s overall design, the phase of the trial, the goal of the trial, the type of cancer, the stage of the cancer, and the type of treatment. 

Other factors can also come into play which may cause delays, such as patient enrollment rates, trial site availability, regulatory approval, data analysis activities, and compiling the results of the analysis.

Clinical trials can take anywhere between several months to a year, and sometimes longer. Trials with a long-term follow-up period are designed to monitor any late-onset side effects, treatment outcomes, and survival rates. Phase 4 trials can even be conducted on an indefinite basis, so it is important to establish timeframes before enrolling in a study.

How successful are clinical trials for cancer?

The success rates of cancer clinical trials can also vary, again, dictated by a number of factors like what phase the trial is in, the cancer type, the treatment being administered, etc. Treatment may be more or less effective depending on the type of cancer a person has. However, many trials show very promising results for a wide range of cancer types, resulting in the approval of new and effective treatments.

Other clinical trials may yield different outcomes or face unforeseen obstacles that can lead to the discontinuation of treatment. However, this does not mean the clinical trial is a failure, as this research and data may be of use when tackling different forms or stages of cancer.

The effectiveness of the clinical trial can be affected by its overall design, the patient selection, the dosing, or other complexities that may impact the treatment’s effectiveness. Ultimately, a cancer clinical trial aims to gather vital information and better understand cancer and how it can be treated, even if a specific trial does not deliver the intended results.

Which stages of cancer can participate in a clinical trial?

Clinical trials for cancer are designed for patients who are at various stages of the disease, with some focusing on the early stages of cancer and some on the latter. This means that regardless of the stage of your cancer, you can still participate in a clinical trial, depending on the goal of the individual study.

Eligible cancer stages may include:

  • Early Stage (I and II): Individuals who have localized cancer, which means the tumor has not spread from a specific area or organ. These clinical trials are designed to assess the effectiveness of new treatments, and their potential side effects, as well as to determine the overall safety of the treatments. 
  • Locally Advanced (Stage III): In this stage, the cancer has spread to nearby lymph nodes or tissues but has not metastasized in other, more distant organs. These trials aim to improve patient outcomes by combining treatments like surgery, radiation, and chemotherapy. 
  • Metastatic (Stage IV): The cancer has spread to distant organs or lymph nodes. Trials for Stage IV cancer involve the testing of new drugs, immunotherapies, targeted therapies, and other forms of treatment in an attempt to shrink the metastatic tumor. 
  • Recurrent or Relapsed: The cancer has returned in this stage following a previous treatment. For recurrent cancer, trials are designed to evaluate new therapies, combinations of therapy, and targeted, personalized approaches.
  • Advanced Cancer: In this advanced stage, the cancer may have progressed to the point where it is terminal and cannot be cured. Therefore, clinical trials for advanced cancer are generally focused on enhancing the quality of life of patients and improving palliative treatment options. 

Questions to ask your healthcare team

It is always important to consult with your healthcare providers before agreeing to participate in a clinical trial, discussing the potential risks and benefits. You should determine the potential value of the cancer trial and your overall goals before making any decision regarding treatment.

Here are some questions that you may want to ask your healthcare team about clinical trials:

  • What type of cancer do I have?
  • What stage of cancer do I have?
  • Are you aware of any specific trials that are available for the type of cancer I have?
  • Are there any specific biomarkers that I should be tested for to help me determine my eligibility for a cancer clinical trial?
  • What are the potential benefits of participating in a clinical trial for cancer?
  • What are the possible side effects that I may experience?
  • Have any clinical trials been conducted previously for this drug/treatment involving people with the type of cancer I have?
  • Will I be told if I am receiving an experimental treatment or a standard treatment?

When should I think about a clinical trial for cancer?

Taking part in a clinical trial for cancer may be a beneficial treatment option for you following a cancer diagnosis. The best way to understand the benefits of a trial and understand your options is to discuss the possibility with your doctor, nurse, or healthcare provider. 

You may be suitable for a cancer clinical trial if:

  • You have been diagnosed with cancer and it has spread to other parts of the body.
  • Your cancer has returned following primary treatment.
  • You are interested in receiving the latest cancer treatments.
  • You have a rare cancer that has proven difficult to treat.
  • Previously successful cancer treatment has stopped working.
  • Your cancer requires long-term treatment or ongoing treatment for the rest of your life.
  • Your cancer has significant side effects and the proposed trial is designed to reduce their impact.
  • You are interested in playing a key part in cancer research and advancing new treatments.

Who is eligible for cancer clinical trials?

Before a person can enroll in a cancer clinical trial they must first meet the eligibility (inclusion) criteria that is set by the research team and trial sponsor. All clinical studies have strict criteria regarding who can and cannot participate. This is to ensure maximum safety throughout the study.

For cancer clinical trials, the inclusion and exclusion criteria typically depend on:

  • The type of cancer a person has and the stage of their cancer.
  • Previous treatments that have been administered.
  • The results of specific lab tests and evaluations.
  • The medication a person has been taking.
  • Other medical conditions a person may have.
  • Whether a person has previously been diagnosed with cancer.
  • A person’s general lifestyle, including overall health and well-being.
  • Factors such as a person’s sex or age.

Are clinical trials for cancer free?

Clinical trials are not always free for participants and any costs incurred depend on a number of factors. For example, the trial sponsor (the pharmaceutical company, academic institution, or government agency) may cover most of the expenses but not all. The location of the trial could also increase expenses if a participant lives far away and is required to visit the trial site frequently, but the costs of traveling to the trial location are not covered.

Some factors that could impact costs associated with participating in a cancer clinical trial are:

  • The Cost of Treatment: The trial sponsor will often cover the cost of any experimental treatment during the trial, with the drug and treatment provided at no cost to the participant. However, this might not always be the case and it is important to thoroughly research which treatment costs are covered before participating.
  • Standard of Care Costs: The costs linked to standard treatment or care that are part of the clinical trial are typically covered by the individual’s health insurance. Although this may also be covered by the trial sponsor in some cases. Make sure to check with your insurance and trial sponsor prior to taking part in a clinical trial to ensure the treatment being studied is covered in full.
  • Study-Related Procedures and Tests: Any procedures, tests, or other medical services that are required by the trial are usually covered by the trial sponsor. This usually includes blood tests, additional scans, biopsies, and medical consultations. However, check with the trial sponsor to ensure there are no additional tests or procedures that need to be conducted prior to taking part in a trial that might not be covered.
  • Other Medical Costs: There may be some costs associated with managing side effects or any complications as a result of the treatment. These costs are likely to be covered by the trial sponsor but it doesn’t always have to be the case that they are covered in full, depending on the side effect.
  • Travel and Accommodation: Some trial sponsors may reimburse participants for travel and accommodation expenses, although this is not always the case. 
  • Insurance Coverage: Anyone participating in a cancer clinical trial is advised to have health insurance to cover the cost of routine medical care or any unforeseen events during the study.
  • Costs Not Covered: Costs that are generally not covered by the trial sponsor may include unrelated medical care, deductibles, co-pays, and any other out-of-pocket expenses.

Before consenting to participate in a clinical trial, you should carefully review all details of the study, including expenses that are and are not covered by the sponsor. The research team will disclose full details of what is covered during the trial while addressing any financial concerns you may have.

Questions to ask about a cancer clinical trial

It is essential to gather as much information as possible regarding the clinical trial before agreeing to take part in one. This allows a person to make an informed decision about whether the benefits outweigh the potential risks, and whether the trial aligns with their overall treatment goals.

Here are some important questions to consider asking the trial research team:

About the trial and treatment

  • What is the overall purpose of the clinical trial/study?
  • What phase is the clinical trial in? (1, 2, 3, or 4)
  • What stage of development is the experimental treatment in?
  • How does the experimental treatment work?
  • How is the experimental treatment administered? (medication, injection, infusion, etc)

About eligibility and participation

  • Do I meet the inclusion criteria for this trial?
  • Will participating in this study affect my current cancer treatment plan?
  • What tests and assessments will be performed during the trial?

About the risks and benefits

  • What are the possible benefits of participating in this trial?
  • What are the potential risks involved in the study?
  • Are there possible side effects that I should be aware of?

About the trial duration and commitment

  • How long is the trial expected to last?
  • What is the level of time and commitment that is required of me?
  • How often do I need to visit the trial site or other locations for assessment?

About placebos and randomization

  • Is there a possibility that I will receive a placebo in this trial?
  • Will group assignments be completely randomized?
  • What are the chances of me being assigned to the experimental treatment group?

About alternative treatment and options

  • What standard cancer treatment options are available to me?
  • Are there other treatment plans that I should consider instead?

About participation, withdrawal, and follow-up

  • Can I withdraw from the trial at any point? And what are the consequences?
  • What happens once the trial has finished?
  • Will I receive follow-up care or additional treatment options?

As well as discussing the clinical trial with the trial team, you should also speak with your loved ones about the risks and benefits before making a decision.

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Before participating in any clinical trial, it is important to be fully informed and ask the right questions. Find a full list of questions to consider asking before taking part in a clinical trial in our comprehensive guide!

Questions to Ask Before Participating in Clinical Trials

The importance of diversity in clinical trials for cancer

In the past, many groups of people, such as Hispanic people, people of color, women, and older adults have been underrepresented in clinical studies for cancer, resulting in a lack of diversity in the results. This is why trial teams now look to include a more diverse range of people to show that new treatments can work across the wider population.

This is important for a number of reasons, for example, statistics show that African American people have the highest cancer death rate. Cancer is also the leading cause of death among Asian Americans. Hispanic people, both men and women, are also twice as likely to die from liver cancer than non-Hispanic Caucasians. 

Furthermore, Native American/Alaskan Natives have the highest death rate when it comes to colorectal cancer and African American women have a higher risk of dying from breast cancer than white women. African American men also have a higher rate of developing lung cancer than white men.

Statistics such as these are why clinical trials need to focus on diversity to improve medical knowledge of the entire population. Clinical trials can show how new treatments can be effective for different races, genders, and age groups.

How to find a clinical trial for cancer

Many people are unaware of the treatment options provided by clinical trials even though they are a viable solution that may offer significant benefits. This is why it is important to ask your healthcare provider about what ongoing clinical trials are available that may be suitable for you. Another option is to call a patient advocacy group that is related to your cancer type and ask about any clinical trials that they are aware of.

Alternatively, it can also be a good idea to check government websites and specialized clinical trial platforms, where you can apply to enroll in a clinical trial directly.

Here are steps to find cancer clinical trials:

  • Browse clinical trial databases such as ClinicalTrials.gov, Cancer.gov, and the World Health Organization's International Clinical Trials Registry Platform (ICTRP).
  • Speak with healthcare providers and relevant institutions who may be able to provide information regarding ongoing cancer clinical trials.
  • Refer to the websites of academic institutions and universities or phone them directly.
  • Discuss possible options with your oncologist.
  • Contact patient advocacy groups and non-profit organizations.
  • Search for cancer research networks or groups that specialize in providing active treatments in clinical trials. Examples include SWOG Cancer Research Network, ECOG-ACRIN Cancer Research Group, and NRG Oncology.
  • Attend various cancer research conferences or webinars

How to find clinical trials for cancer that don't use placebos

Thorough research is required when finding cancer clinical trials that do not use a placebo, with the details of the trial needing to be fully understood. Placebos are used in many trials as a control mechanism, helping to provide a comparison for the experimental treatment. However, some studies for cancer research use an active treatment instead, especially when an effective standard of care exists.

When searching for clinical trials that do not use placebos, follow the steps in the previous section, using search terms specifically for cancer clinical trials that involve active treatments.


Clinical trials for cancer are vitally important for improving medical knowledge of the disease and finding new drugs and treatments that can help to provide cures, manage symptoms, and enable early detection.

Each trial has set inclusion criteria that dictate who can participate in a trial, such as the type of cancer and its stage. This criteria also encourages more diversity so new, experimental treatments can be applied to a wider population.

Participating in a cancer clinical trial can be a beneficial option for those seeking the latest treatments. It's essential to thoroughly research and consult with your healthcare provider to understand the potential benefits, risks, and eligibility criteria of the trial.

There are several ways to find a clinical trial, including consulting healthcare providers, browsing clinical trial databases, and contacting patient advocacy groups.

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