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QUESTION: What is a clinical trial?

New cancer treatments usually undergo many years of testing before they are approved for standard use in patients. The last steps in the testing process are called clinical trials, which studies how new treatments work in patients. At Mission Hope Cancer Center, we participate in many clinical trials for many types of cancer.

These trials take place in four phases with each phase asking a different question and gathering data to support further research. The phase specifies how much research has been done and identifies how patients participate in the study.

Phase I

These trials usually test a new investigational drug in humans for the first time, after it has been studied in the lab. Phase I studies are closely monitored and conducted in patients or normal volunteer subjects. These studies can also be used to evaluate an approved drug at a higher dosage or in a different disease.

Twenty to 80 people usually participate, and patients with different types of cancer may be allowed into the trial. Researchers are focusing on the safety of the treatment, studying the best way to administer the treatment, the maximum safe dose and the frequency the treatment can be given.

One of the benefits of participating in a Phase I trial is being one of the first patients to receive a new investigational drug that might prove effective against cancer. However, these trials also carry risks because no one knows the exact effectiveness or what side effect(s) may or may not occur.

Phase II

Phase II trials are studies conducted to evaluate the effectiveness of the investigational drug for a specific indication. These trials determine side effects and risks associated with the investigational drug. These typically enroll less than 100 patients and recruitment can take up to two years.

Phase III

If preliminary data from the Phase II studies suggests effectiveness and safety, Phase III trials are performed. These trials are expanded controlled and uncontrolled trials.

The participants may or may not be randomized to a specific treatment arm; for example, standard of care vs. investigational drug.

The risks associated with Phase III trials can include adverse side effects that are worse than standard treatment or even possibly that the investigational drug is less effective than the standard treatment. Typically, enrollment is between 100 and several thousand people. Recruitment for these trials can take three to four years.

Phase IV

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These trials are conducted after a new treatment has been approved for standard use and are used to measure the long-term safety and effectiveness of the treatments.

Patient participation

Due to our affiliation with UCLA, Mission Hope Cancer Center offers many clinical trials for many different types of cancer.

After receiving a thorough explanation of the possible risks and benefits of the treatment being studied, patients can decide whether or not to participate in a clinical trial. Patients who participate in a clinical trial may or may not receive a benefit beyond what they would have received with standard treatment of care, but their participation will add to what is known about their disease and perhaps lead to a cure.

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Your Cancer Answers is a weekly column produced by Marian Regional Medical Center, Cancer Program. Have a question? Email it to

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