Randomized Controlled Trials: Overview, Benefits and Limitations
A randomized controlled trial is a type of clinical trial that is used to evaluate how well new treatments work and how safe they are.
In a controlled trial, the participants are assigned to different treatment groups. Some trial participants receive the new treatment – this is often referred to as the “experimental group.” Other participants are assigned to a “control group.” In some trials, the control group receives a placebo (a treatment that looks identical to the new drug but contains no active medicine). In other trials, including trials for cancer patients, the control group receives the current standard of care.
A randomized controlled trial is a controlled trial in which a participant is randomly assigned to either the experimental group or the control group. Neither the trial doctors nor the participants choose which treatment a participant will receive. Instead, treatment assignment is usually determined by a computer program. The computer program makes sure that the treatment groups are balanced – that the 2 treatment groups are similar in terms of average age, disease severity, and other factors that could affect the trial results. But a given individual’s treatment assignment is decided randomly (by chance) rather than a doctor’s decision or a patient’s preference.
What are the advantages of a randomized controlled trial?
Controlled trials are often used in clinical research because they allow researchers compare outcomes for people in the experimental group with outcomes for people who received either an existing treatment (if one is available) or no treatment. For a new treatment to be approved, there has to be evidence from clinical trials that the treatment has the potential to improve outcomes for patients.
Randomized controlled trials are often considered the gold standard in clinical research because this type of trial design helps prevent bias. Bias happens when the trial results are influenced by choices that people involved in the trial might make, such as who should receive which treatment. If participants are randomly selected for each treatment group, and the groups are well-balanced, then it is more likely that the only variables leading to differences between the groups are the effects of the treatments themselves.
What are the disadvantages of a randomized controlled trial?
From a participant’s perspective, the main disadvantage to a randomized controlled trial is that the participant does not get to choose which treatment they will receive.
Often, and particularly when the trial is enrolling participants with a life-threatening illness for whom an existing treatment is already available, the participant will receive standard therapy, regardless of their treatment group. Participants in the experimental group will receive standard therapy plus the experimental treatment, while participants in the control arm will receive standard therapy alone. The researchers will measure whether adding the new treatment to standard therapy improves outcomes.
From a research perspective, it can be more difficult to recruit participants to join a randomized controlled trial. As such, these trials often taken longer to complete and cost more. And it may be difficult to tell if the participants who choose to join such a trial accurately reflect the larger population of people who might use the treatment once it is approved.