Types of clinical trials

There are three main types of clinical trials.
• Phase I. These clinical trials are designed to determine the maximum tolerated
doses (MTD) of a new drug and to evaluate the side effects. The dose of a new
drug is gradually increased in small groups of children until unacceptable toxic-
ity or side effects are seen. This means that one small group of children gets a
low dose. The next small group gets a slightly higher dose, and so on until an
unacceptable number of patients experience unacceptable toxicities. The highest
dose of a drug that can be safely given to children without unacceptable side
effects is then studied in a Phase II trial.
Phase I studies are done on drugs whose effectiveness against a disease is
unknown, though there is often laboratory evidence to suggest that it may be
effective. These are true experiments. Although an individual child may benefit
from participation, it is much more likely that later patients will reap the full
benefit of the information. All known effective therapies have usually been
exhausted for children asked to participate in a Phase I trial. Parents often enroll
their children in these trials in the hope that a new and untried drug will be
effective, but they need to recognize that the chances are low.
• Phase II. These trials are designed to see if a new drug is active against specific
tumors. Sometimes patients are enrolled when their tumors have relapsed after
other therapies. Occasionally, Phase II trials are designed to test an exceptionally
promising agent against a tumor for which other effective therapies exist. While
the treatments are experimental, there is usually reason to believe that patients
enrolled may benefit.
• Phase III trials. These clinical trials determine if a new treatment is better than the
usual or standard therapy. Some are designed solely to improve survival; others try
to maintain survival rates while lowering toxicity of treatment. In these studies, all
patients are given known effective therapies. Some will derive direct benefit, if a
new arm proves superior to standard therapy. Others will receive the same therapy
they would have received if not enrolled on the study (the standard arm).
The National Cancer Institute (NCI) offers parents several resources to help them
understand the clinical trial process. You can call the National Cancer Institute at
(800) 422-6237 or you can visit the NCI clinical trials web site at http://www.cancer.
gov/clinical_trials/.
The information in the rest of the chapter is about Phase III trials that are reviewed
and funded by the National Cancer Institute. Issues for enrolling in Phase I and
Phase II trials are very different, as are concerns when enrolling in trials sponsored by
private companies.