New cancer treatments typically undergo years of testing before they are approved for standard use in people. The last steps in this testing process are clinical trials, which study how new treatments work in patients.
Cancer clinical trials take place in up to four phases. Each phase asks different questions and gathers data to support further research. The phase indicates how much research has been done and approximately how many people participate in the study.
Phase I trials
Phase I trials usually test a new treatment in humans for the first time, after the treatment has been shown to be safe and effective in laboratory and animal studies. A phase I trial can also be used to evaluate an approved drug at higher doses or in a different disease. Fifteen to 30 people usually participate, and patients with different types of cancer might be allowed to enter the trial. These patients have usually tried other treatments without success.
In phase I trials, researchers focus on the safety of the treatment, studying the best way to administer the new treatment, the maximum safe dose, and how often the treatment should be given. One benefit of participating in a phase I trial is being among the first to receive a new treatment that might prove effective against cancer. However, phase I trials also carry risks, since the effectiveness of the treatment in people has not been demonstrated and no one yet knows what side effects might occur.
Phase II trials
If the new treatment is shown to be safe in a phase I trial, the study progresses to phase II. In phase II trials, researchers continue to test the safety of a new treatment and begin to evaluate how well it works. These trials typically enroll fewer than 100 participants, and eligibility is usually based on which prior treatment(s) participants have received. Recruiting enough participants for a phase II trial may take up to 2 years.
Phase III trials
Treatments that are shown to be effective in phase II trials are further refined and studied in phase III trials. A phase III trial usually determines whether a treatment will be approved for a particular disease and typically enrolls between 100 and several thousand people. These participants are divided into two or more study groups, depending on the research questions being asked.
In phase III trials, researchers try to find out whether the new treatment works better than, the same as, or worse than the standard treatment. Even though only about half the patients in a phase III trial will get the new treatment, those who don’t will receive the standard treatment, which has so far proved to be the best available. Despite a popular misconception, placebos (fake drugs) are rarely used in cancer treatment trials. If a placebo is used, it is given along with the standard treatment.
Risks of participating in a phase III trial can include adverse effects that were not noted in prior studies or are worse than those found in standard treatment. It is also possible that the new therapy will be less effective than the standard treatment. Recruitment for phase III trials can take 3–4 years.
Phase IV trials
Phase IV trials are rare. They 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 treatment.
After receiving a thorough explanation of the possible risks and benefits of the treatment being studied, patients can decide whether to participate in a clinical trial. Patients who choose to take part in clinical trials may or may not receive a benefit beyond what they would have received with standard care, but their participation will add to what is known about their disease and perhaps lead to a cure.
For more information, ask your physician, visit www.clinicaltrials.org, or call askMDAnderson at 877-632-6789.
OncoLog, September 2017, Volume 62, Issue 9