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The goal of a Phase I trial is to find the safest dose of a new drug that patients can receive without creating harmful side effects. During a Phase I trial, the researcher also examines the best way to give a new drug, such as by mouth or intravenously (through a vein).

Throughout Phase I trials, researchers monitor whether the new drug shows any effect against cancer. However, because these trials often are testing drugs for the first time in people, the goal is to find out how to give the drug in a safe way, and not how well it fights cancer.

Phase I trials usually include 15 to 30 people. Usually patients who have undergone standard treatments without success and have no other options are eligible to participate in a Phase I trial.

Typically, patients in Phase I trials are divided into cohorts – small groups of patients – usually around three people. The first cohort receives a low dose of the new drug. Researchers may collect blood or urine samples to measure drug levels. If no severe side effects occur, then a new cohort receives a higher dose of the same drug. The dose increases with each new cohort until the researchers see too many side effects or until they determine the best dose.

If the treatment successfully passes through a Phase I trial, then it will move forward to be studied in a Phase II trial.


The main goal of a Phase II trial is to examine how well the new treatment works to fight a certain kind of cancer. Less than 100 patients usually participate in a Phase II trial. Patients who volunteer for a Phase II trial may have been treated with chemotherapy, biotherapy, surgery or radiation and still need further treatment.

In addition to evaluating how well the treatment works against the cancer, doctors continue to monitor side effects. Since more patients participate in Phase II studies, some of them may experience side effects that patients in the Phase I clinical trial did not have.

If the new treatment seems to be effective against cancer in a certain percentage of patients, researchers may consider it successful enough to continue study in a Phase III clinical trial.


The goal of a Phase III trial is to compare the new treatment with the standard treatment. Researchers track whether a new treatment is better than, the same as, or less effective than the standard treatment.

Phase III trials may include hundreds to thousands of patients around the country or world. In general, each patient enrolled in a Phase III clinical trial has an equal chance of participating in one of two or more arms (groups) of the study.


In a clinical trial with two arms:

The control group receives the standard treatment.

The investigational or experimental group receives the new treatment being tested

Randomization is the process of assigning participants to groups. Randomization helps avoid bias in the clinical trial. Bias occurs when human choices or other factors not related to the treatment being tested change a study’s results.

Neither the patient nor the doctor can choose whether the patient is in the control group or the experimental group. Regardless of which group a patient is assigned to, either he or she will receive the best standard treatment available or the new treatment that researchers believe is as good as, or better than, the standard treatment.


In single blind studies, patients do not know whether they are in the experimental or control group


In double blind studies, neither the patients nor the researchers know which patients are in each group. However, it is important to know that this information is recorded and can be revealed if medically necessary.


The role of the U.S. Food and Drug Administration (FDA) is to make sure medical treatments are safe and effective for people to use. Drug companies must do years of laboratory research before they can begin testing medicines in humans. Researchers submit their clinical trial results to the FDA, and based on the information, the FDA may approve the drug or treatment. Then it becomes available to all patients and sometimes becomes the new standard treatment.


In Phase IV trials, researchers study drugs and/or treatments that have already received FDA approval. The goal of Phase IV trials is to study how safe and effective a drug or procedure is over time. These trials occur after the treatment has been put on the market in order to monitor effects of long-term usage and how it affects certain population groups. If dangerous side effects are found, the drug or treatment is taken off the market.

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