The continuing search for effective cancer treatments begins with research.
A clinical trial is a study conducted with cancer patients in order to evaluate a new treatment. Before any new treatment is tried with patients, it is studied in laboratories which helps to identify new methods that are most likely to succeed, and help demonstrate safety and effectiveness. The best results of research are then tested in studies with patients, ideally leading to new and better treatments.
All clinical trials are conducted in the same places that provide standard treatment for cancer. With any new treatment there may be known or unknown risks, and importantly, potential benefits.
Clinical trials are divided into different stages called phases. The earliest phases may look at whether a treatment is safe or the side effects it causes. Later phases test whether a new treatment is better than an existing treatment.
Phase 1 trials
Phase 1 trials aim to look at doses and side effects. After laboratory testing shows that a new treatment might help treat cancer, phase 1 trials are done to find out the safe dose range; what the side effects are; how the body copes with the drug; and if the treatment shrinks the cancer. This work has to be done first, before the potential of a new treatment can be tested to see if it works.
This phase of a trial is usually small and recruits only a few patients. Patients are usually recruited slowly into phase 1 trials which can result in phase 1 trials taking a long time to complete.
Phase 2 trials
Not all treatments tested in a phase 1 trial make it to a phase 2 trial. Phase 2 trials aim to find out if the new treatment works well enough to be tested in a larger trial; which types of cancer the treatment works for; more about side effects and how to manage them; and more about the best dose to use. Although these treatments have been tested in phase 1 trials, there may still be side effects that the doctors don't know about.
Phase 2 trials are often larger than phase 1. There may be up to 100 or so people taking part. Sometimes in a phase 2 trial, a new treatment is compared with another treatment already in use, or with a dummy drug (placebo). If the results of phase 2 trials show that a new treatment may be as good as existing treatment, or better, it then moves into phase 3.
Phase 3 trials
In this phase, the trials compare the new treatment with the best currently available treatment (the standard treatment). These trials may compare a completely new treatment with the standard treatment; different doses or ways of giving a standard treatment; and a new way of giving radiotherapy with the standard way.
Phase 3 trials usually involve many more patients than phase 1 or 2. This is because differences in success rates may be small. So, the trial needs many patients to be able to show the difference.
Phase 4 trials
Phase 4 trials are done after a drug has been shown to work and has been granted a licence. The main reasons for running phase 4 trials are to find out more about the side effects and safety of the drug; what the long term risks and benefits are; and how well the drug works when it is used more widely.