Understanding Cancer Research Studies
"A new study finds that eating 9 vegetables daily prevents colon cancer." "Results
of a clinical trial show tamoxifen is effective in preventing breast cancer in high-risk
women." Do you wonder what a clinical trial or an epidemiological study is after hearing
With more and more of these studies appearing in the news, you have to understand
some basic lingo to make heads from tails. Here is a primer on health research so
you can follow along and better understand health headlines.
Making the connection
Americans are living about 20 years longer than a century ago, thanks to medical advances.
But reaching a ripe old age comes with a catch. It also means developing chronic diseases,
such as heart disease, cancer, and diabetes. Researchers are constantly searching
for answers on how to prevent and treat disease, and improve the quality of life for
those with disease.
Theories on the causes of disease may start in a laboratory. Scientists study cells
in test tubes (also called in vitro) or animals to test their theories. They can easily control the environment of the
cell or animal being studied. This means that the scientist decides exactly what the
cell or animal is exposed to, such as temperature, diet, or chemicals. If that produces
an interesting finding, scientists may propose a human study. This is because what
happens in an animal may not happen the same way in people.
Researchers can also create theories about causes of disease by looking at large populations
of people. For example, they may wonder why American women have higher rates of breast
cancer than Japanese women. Researchers may compare the women's diets, amount of activity,
or stress levels to find a reason.
Unfortunately, "people studies" are complicated. They are expensive, often take a
long time, and present many factors not seen in a laboratory. There is the type of
environment to consider (urban, rural); lifestyle factors (diet, amount of physical
activity); psychological influences; family genes; and the list goes on.
However, research studies have helped to reduce many health risks. For instance, researchers
have found that a diet lacking in certain vitamins and minerals causes specific diseases.
They have discovered the link between smoking and lung cancer. Many infectious diseases,
such as chickenpox and measles, are now preventable with vaccines.
Types of human studies
Epidemiological or population studies
Epidemiological or population studies look at a large group of people in a specific
region. Researchers will observe a disease that is present and study why people have
it. Therefore, they are sometimes called observation studies. They find links between an exposure and a disease. Here are 3 common types of these
Cross-sectional studies are useful in seeing how common a disease is in a certain
region. Researchers may start with a cross-sectional study to decide if another type
of population study is needed later on.
A group of people is gathered to observe certain information at one point in time.
For example, researchers may observe a thousand people in the state of California
to see who has lung cancer on June 1, 2015. These studies are inexpensive and quick.
However, since they are like instant "snapshots" of people, they can't explain what
led up to some people getting lung cancer.
These studies are like looking at people's diaries. They gather two groups. One group,
the cases, has the disease being studied. The other group, or controls, doesn't have
the disease, but is very similar to the cases in other ways. For example, they may
be the same age, live in the same area, or have other similar lifestyle habits.
Researchers then look back into the past, usually relying on the participants' memories,
to see any differences between the cases and controls. The researchers look at a specific
exposure, or potential link to the disease. Did the two groups eat differently? Were they
exposed to certain chemicals? If an exposure stands out in only the cases or only
the controls, that exposure could be linked to the disease.
This type of study looks ahead. Researchers choose an exposure and the disease (or
condition) expected to happen because of the exposure.
A large group of people, called a cohort, is observed by researchers over a period
of time to see who develops the disease and who does not. They could be followed for
any length of time; for instance, 5 years or more than 20 years.
Clinical trials are another type of human study. Clinical trials usually, but do not
always, look at treatments.
Cancer clinical trials work with a group of people who have something in common (for
example, a type of cancer or risk factor). Researchers decide on an agent or intervention
for the group that may affect the disease or problem being studied. Examples of agents
are a new medicine or high-dose vitamin.
You may hear the term placebo-controlled. This is when half the group is given an agent or intervention and the other half
a placebo. A placebo is a fake or "dummy" pill—something that looks like the agent,
but has no effect at all. A placebo is usually not used when there is already an effective
treatment for the condition. With cancer, an agent or intervention is usually compared
to a standard cancer treatment. Sometimes cancer prevention trials use placebos, such
as looking at the effects of a high-dose nutrition supplement on the prevention of
cancer. One group of people would get the supplement and another group the placebo.
If two groups are used (receiving either an agent or a placebo), it is important that
the trial is fair and the groups are as equal as possible. So the scientists may "blind"
the participants (single-blind) or even themselves (double-blind), so that no one
knows who is getting the placebo or the agent. They may also randomize the participants
in the beginning. This means they will use an unbiased system, often a computer, to
randomly select who will get the agent being tested.
New cancer treatments develop in clinical trials through 3 phases:
Phase I gives a small number of people a new treatment or medicine, observes side
effects, and finds the best dose and way to administer the agent. People who are very
sick and not responding to other treatments may enroll here.
In addition to these 3 phases, the American Cancer Society identifies a Phase 0 for
drug trials. Phase 0 clinical trials explore how a new medicine may work. Phase 0 information
is included because more cancer volunteers may be asked to take part in these studies
in the future. The goal of this phase is to speed up approval of a new medicine.
Humans are used in this trial, but Phase 0 is not like the other 3 clinical trial
The biggest difference between Phase 0 and the other phases is that the patient has
no chance of benefitting from this trial. People in the future are the ones who will
benefit from Phase 0 research.
Phase 0 trials are exploratory and the medicine is given in very small doses and for
a short period of time.
Researchers look for medicine absorption, whether the medicine reaches the tumor,
how the cancer cells respond, and if there are any adverse medicine actions within
Phase 0 trials are very small (often with fewer than 15 people) and are not widely
used. Phase 0 research is not a requirement for testing a new medicine.
Clinical trials for new cancer treatments are always emerging. Talk with your healthcare
provider about whether you may benefit from a clinical trial.
Visit the National Cancer Institute's Cancer Trials website to find specific clinical trials. Or call the National Cancer Institute's Cancer
Information Service at 800-422-6237 for more general information about clinical trials.
You can also learn more about trials on the www.clinicaltrials.gov website, a service
of the National Institutes of Health.