By A.J.S. Rayl

Clinical trials are research studies that test new ways to prevent, diagnose or treat disease. It is through a series of increasingly elaborate clinical trials, conducted in phases, that we prove the value and safety of any given treatment or drug. But for cancer patients, clinical trials represent not just the quest for evidence, but also hope. Though clinical trials are, by definition, experiments and thus long shots, they sometimes hold the best chance of survival for those with advanced disease.

"Ultimately, the decision to participate in a trial is personal," says oncology nurse Andrea Denicoff, a cancer clinical trials specialist at the National Cancer Institute. The trick is finding a trial that's right for you, something easier said than done. While personal physicians often refer patients to appropriate studies, it's impossible for any one doctor to have a handle on them all. Instead, it usually falls to the patient to investigate the options and, guided by professional input, chart her own path. To assist in that effort, we provide a road map to the complex but potentially rewarding clinical trial terrain.

Types of Trials

Clinical trials address everything from treatment and diagnosis to prevention.

Treatment trials evaluate the effectiveness of a new drug or treatment, or a new way of using a standard treatment. These trials test chemotherapies, vaccines, or new approaches to surgery or radiation treatment.

Prevention trials investigate different ways to reduce the risk of developing cancer. Prevention trials may be conducted with healthy people who have never had cancer or cancer patients in remission hoping to prevent a recurrence.

Screening trials study ways to detect cancer. Often these trials seek to determine whether finding cancer before it causes symptoms decreases the chance of dying from the disease. These investigations involve people who do not have any symptoms of cancer.

Diagnostic trials test procedures for identifying cancer more accurately and at an earlier stage. Usually conducted with people who have signs or symptoms of cancer.

Genetics trials examine the role that genes play in cancer risk or response to treatment. Usually conducted with specific populations, these trials seek genetic mutations by looking at DNA from blood or tissue samples. Depending on the study, people who participate may or may not have cancer.

Adjuvant trials test a treatment meant to augment but not replace the current standard of care. Adjuvants are usually given after the primary treatment to increase the chance of a cure or prevent relapse.

Understanding the Phases

Human drug trials are conducted in four phases, each one part of the effort to prove a treatment effective and safe.

Phase I: Is it safe?
The classic Phase I clinical trial is conducted to determine the maximum tolerated dose and characterize the side effects. In these trials the dose is usually increased a little at a time, with different cohorts or groups receiving differing amounts of the treatment, in order to find the highest safe dose.

Many Phase I trials may look for side effects or evidence that a drug is absorbed, metabolized, or otherwise biologically active in the patient. Other Phase I trials test the best way to give the new treatment, whether by intravenous infusion, injection, or mouth.

A Phase I trial is not designed to show whether the treatment is effective, but because an experimental drug is chosen for its promise, patients may still benefit. Phase I treatment trials for cancer usually do not have control groups. Since little is known about the possible risks and benefits of the treatments being tested, these first human trials usually include only a small number of patients (15 to 25) who have not been helped by other treatments.