Phase I Trials
Phase I trials are the first use in humans and the goal for these trials is to determine the best dosing schedule — the amount of drug, route of administration and dose frequency. Particular attention is directed at learning about the drug or treatments side- effects and any toxic effects. Since these Phase I agents have a limited track record of anti-tumor activity, Phase I trials are usually only open to patients after more established therapies have failed. Initially, low doses that are likely to be non-toxic are used and the dose of the drug is subsequently increased while side effects are carefully measured. Usually between 15 and 50 patients are entered on a Phase I trial. Responses to treatment are hoped for and noted, but the true evaluation of clinical activity against the cancer awaits the Phase II trial.
Phase II Trials
Phase II trials evaluate whether a new drug or treatment is effective against specific types of tumors, for example epithelial ovarian cancer. The dose that was determined to be safe and tolerable during the phase I trial is used. Usually 20 to 200 patients are entered in a Phase II trial in a stepwise fashion. If there are no tumor responses in the first group of patients, the trial is usually closed. In contrast, if there have been a number of patient responses in the first few patients, the trial is often expanded to help better define the percentage of patients who will respond and to help better define the side effects and toxicities.
Phase III Trials
Phase III trials are the largest and most important. Several hundred to a few thousand patients are needed for most Phase III trials. The purpose of these trials is to evaluate whether a new treatment, either on its own or added to another treatment (commonly referred to as the experimental arm) can improve outcomes when compared to an already proven treatment (commonly referred to as the standard treatment or control arm). With experimental cancer treatments, the Phase III trials usually aim to learn whether patients live longer or have longer remissions with the new treatment compared to the standard therapy. While it is the desire and hope that new treatments in Phase III trials will produce a superior outcome, such is not always the case. Sometimes the outcome is no better but the toxicities are worse although this is rare.
On very rare occasions, despite hopeful evidence from Phase I and II trials, the experimental treatment turns out to be inferior to the standard treatment. However, virtually all of the celebrated standard treatments offered today were discovered through clinical trials conducted over past years and decades.
In addition to the three clinical trials phases, there are different types of clinical trials: (1) prevention trials, (2) screening trials, (3) diagnostic trials, (4) treatment trials, (5) quality of life/supportive care trials and (6) genetics trials.