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Clinical Trials FAQs

A clinical trial (also called a clinical study) is a type of scientific research study that tests how safe and effective new medical approaches are in human participants. A trial may involve testing of a new screening, prevention, diagnostic or treatment approach for a particular disease such as cancer.

The following frequently asked questions provide information about clinical trials — what they are, why they are important, and their benefits and risks. 

If you have questions or would like more information, please contact the UMass Cancer Center at

What are clinical trials?

Researchers often need to find answers to critical health-related questions. To find these answers, they start by doing laboratory and animal studies (known as preclinical studies). After many years of careful preclinical testing, only the studies with the most promising results are then moved on to clinical trials. A clinical trial is a type of scientific research study that is done with human participants. People who choose to participate in clinical trials may have a specific disease, or they may be healthy volunteers.

The purpose of a clinical trial is to evaluate the effects of a new intervention on human health and disease. Interventions can be in the form of a drug treatment (such as chemotherapy, immunotherapy, or targeted therapy), a treatment strategy (such as maintenance therapy or concurrent therapy), a medical device, a procedure (such as surgery or radiation therapy), or a behavioral program involving diet and exercise. A clinical trial may also be used to identify novel markers for diagnostic and prognostic predictors of outcome for a disease. Typically, a clinical trial sponsor, such as a pharmaceutical company or a private organization, will initiate and pay for the trial, while a clinical researcher known as the principal investigator has primary responsibility for carrying out and supervising the clinical trial protocol.

Why are clinical trials important?

Clinical trials are critical for helping researchers and doctors find new and better ways to detect, diagnose, control, and treat diseases, including cancer. The results from clinical trials can lead to the approval of new, safe treatments that are more effective at fighting cancer than are currently available treatments. They can also discover new ways of using existing treatments. Participants who volunteer for clinical trials play a vital role in advancing knowledge about cancer, developing new tools and treatments in cancer medicine, and ultimately helping current and future cancer patients.

What are the different phases of clinical trials?

Clinical trials are done in several progressive phases, with each phase aiming to answer different questions.  

Phase I: Is it safe?  Phase I clinical trials are the first step in testing a new intervention in human participants. The focus in this first step is on ensuring safety and identifying side effects. A phase I trial allows a clinical researcher to see how the new intervention affects the human body and to find the best dosage range and dose schedule that can be given safely without serious side effects.

Phase II: Does it work?  Phase II clinical trials are the second step in the testing process, where researchers look at how the intervention affects the disease and whether the intervention is effective. The intervention is now tested in a larger group of human participants (up to several hundred people), using the dosage range and schedule determined to be safe in the phase I trial. Researchers also continue to evaluate the safety of the intervention in this stage.

Phase III: Is it better?  Phase III clinical trials are done only after the results of the phase II trial show promise. These trials are done in an even larger number of human participants (300 to 3,000 people) who are assigned to different groups (also known as arms). Some of the participants are assigned to receive the intervention (the study group), while others are assigned to receive a commonly used intervention or the current standard-of-care intervention (the control group). Participants do not get to choose which group they are assigned to. Rather, the researchers assign them to groups randomly; this is known as a randomized clinical trial. Comparing the results from the study group versus the control group allows the researchers to see whether the effectiveness and safety of the new intervention are better, the same, or worse than other interventions already being commonly used.

Phase IV: Which questions remain to be answered?  Phase IV clinical trials are done after the new intervention — which proceeded successfully through phases I, II, and III — has been approved by the Food and Drug Administration (FDA). These trials are done with several thousand participants. At this point, even though the intervention is now available for patients to receive from their doctors, patients can still participate in phase IV trials to help researchers answer important remaining questions. For example, a phase IV trial might look at the intervention’s safety over a longer period of time, its cost effectiveness, or whether it affects patients’ longevity or quality of life.

What are “controlled” clinical trials?

A controlled clinical trial is a type of clinical trial that includes a control group of participants that is used as a comparison to the study group of participants. While the study group receives the intervention, the control group may receive a different intervention (such as a standard-of-care intervention), no intervention, or an inactive placebo. When a controlled clinical trial includes a control group that receives a placebo, it is referred to as a placebo-controlled trial.

What are “blinded” clinical trials?

A clinical trial is “blinded” when participants do not know which group they have been assigned to. In other words, they are not aware of whether they are part of the study group receiving the new intervention being tested, or whether they are in the control group receiving a standard-of-care intervention or an inactive placebo. Some clinical trials go one step further to be "double-blind." In this case, neither the participants nor the researchers know who is receiving the intervention and who is in the control group. Clinical trials are often done in a blinded way so that neither the participants' nor the researchers' expectations about the intervention can influence the results.

How is the outcome/success of a clinical trial measured?

At the end of a clinical trial, researchers assess the effects of the intervention on the health and survival of participants with a disease such as cancer. To do this, they use specific measures of how well the intervention worked to improve participants’ outcomes. One such measure is known as event-free survival, which is the length of time that participants remain free of complications and events after undergoing primary treatment for their disease. Researchers may also look at progression-free survival, which is the length of time that participants do not show signs of disease progression (do not get worse) during and after treatment. Another measure, called overall survival, is the length of time that participants are still alive following diagnosis or treatment.

Researchers can prioritize any of these measures — event-free survival, progression-free survival, overall survival, or another outcome measure — as the outcome that is the most important for evaluating how well an intervention worked. This is known as the primary outcome measure or primary endpoint, which is essentially the main finding of the clinical trial. Researchers often look at additional outcomes to provide supplemental information about the effects of an intervention and to help interpret the main finding. These are known as secondary outcome measures or secondary endpoints.

What are the benefits and risks of participating in a clinical trial?

One of the main benefits of participating in a clinical trial is that patients can gain access to a promising new intervention that is not yet available through their regular healthcare providers. Some interventions in clinical trials may be better than current standard interventions. However, even if participants do not personally benefit from the clinical trial, their participation paves the way for advances in medicine and helps future patients.

Clinical trials have risks. A new intervention has the potential to cause unknown side effects or other health-related risks, or can cause inconveniences such as more frequent office visits and testing, as well as additional time and travel commitments. Before enrolling in a clinical trial, volunteers agree to participate by giving informed consent, described in more detail below.

Is it safe to participate in a clinical trial?

The safety, rights, and privacy of clinical trial participants are protected by local, federal, and international laws, and oversight committees routinely monitor clinical trials to ensure protection of participants’ rights. Before people agree to participate in a clinical trial, researchers are required to provide detailed information about the clinical trial’s purpose, procedures, and possible risks and benefits of participation. This is known as informed consent. Researchers will also inform participants of new benefits, risks, or side effects found during the course of the clinical trial.  Because participation in clinical trials is entirely voluntary, participants can choose to stop participating at any time, for any reason. For more details, see the Informed Consent for Clinical Trials page from the Food and Drug Administration (FDA).

Am I eligible to participate in a clinical trial?

Every clinical trial has its own set of criteria for who is eligible to participate (inclusion criteria) and who is not (exclusion criteria). This is a standard, required practice when researchers are designing their clinical trials. In order to join a clinical trial, a volunteer must meet the clinical trial’s inclusion criteria. Having any of the characteristics listed in the exclusion criteria will disqualify a volunteer from participating.

The inclusion and exclusion criteria are related to a variety of participant characteristics such as age, stage of disease (as determined by cancer staging), presence of co-occurring conditions, or previous treatment history. The purpose of having inclusion criteria is to identify the appropriate population in which researchers expect that the effect of the intervention can be demonstrated. The purpose of having exclusion criteria is to prevent certain participant characteristics from interfering with the evaluation of the intervention or increasing the risk of an unfavorable outcome. These eligibility criteria vary from one clinical trial to the next, and can be found in the clinical trial’s protocol.

How do I find cancer clinical trials at UMass?

Your doctor may offer you the option to participate in a clinical trial as part of your treatment plan. However, interested patients and healthy volunteers can also do their own search on the UMass Cancer Center Clinical Trials page for trials that are currently recruiting participants. The UMass Cancer Center offers the largest selection of advanced clinical trials in Central Massachusetts.

The trials are designed and developed by cancer experts nationwide (the principal investigators) and are offered at UMass as a clinical study site.

If you have questions, contact the UMass Cancer Center.