Clinical Trials are medical research studies using human volunteers. They are intended to add to medical knowledge. In a clinical trial participants receive specific treatment according to the research plan to generate new information on e.g. treating cancer with a new drug. These studies usually are led by a principal investigator who has a team of specialist and funded by various organizations including government, health insurance or pharmaceutical companies. To participate in a clinical study one has to pass the eligibility criteria of the study. One can search for a specific study for example under https://clinicaltrials.gov/ .
Trial Phases
To decide whether a new drug or treatment option is successful it has to pass several testing phases. These phases are discussed in the following section for cancer research
Phase 0
Only very few people take part in Phase 0 trials receiving only a small dose of the new drug. This dose is usually to small to cure cancer, but also too small to produce side effects. The aim of this phase is to test whether the new drug works as expected. The researchers investigate if the drug reaches the cancer, how it behaves in the body and how the cancer cells respond to the drug. Extra scans and blood and tissue samples are used to analyze the results.
Phase 1
In this phase only a small amount of people with any kind of cancer is recruited as well over a long phase. This phase is executed if laboratory tests or phase 0 suggested that a new treatment might help fighting cancer to find out the right dose of a drug, the possible side effects and if the drug shrinks the tumor. Several groups undergo the phase with gradually increasing doses until the researchers find the best amout. This is also called a dose escalation study.
Phase 2
Phase 2 is designed for a larger group of people up to around 100. Participants can be limited to specific kinds of cancer. However this is only an option. Phase 2 tries to find out if the treatment is valid enough to be tested in an even larger phase 3, to which cancer types the treatment is effective and to gain additional knowledge on side effects and the optimal dose. In some phase 2 trials the new treatment is compared to an already existing one or a placebo and the groups can be randomised.
Phase 3
Phase 3 is the last stage before a new drug is approved. Therefore the new treatment is compared to the currently best available treatment. This can be a completely new treatment or a new dosage or way of giving a standard treatment. Furthermore Phase 3 includes a lot more people usually in randomised groupds than the previous phases, because the differences in in success rates may be small. If a treatment passes phases 3 it is granted a license
Phase 4
These trial are executed to find out more about the side effects, the long term risks and safety of the drug and how well the drug works if it is employed in a broader audience. The license can still be removed if significant side effects occur.