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A placebo is a something that looks like a drug but that doesn’t contain any active ingredient.  Placebos are used in clinical trials only where there is no standard treatment for a particular type of cancer.  These trials aim to test whether the drug being studied is more effective than no treatment at all.

To make a fair comparison and reduce bias, patients receive, on a random basis, either the drug being tested or a placebo which looks the same as the drug.  Usually neither the doctor carrying out the trial nor the patient knows whether the patient is taking a placebo or the active drug.  In the term used in research, this is a ‘blinded trial’.  At the end of the study, the trial is ‘unblinded’ and the patient (and the doctor) are informed whether or not they were using the active drug.  If the patient becomes unwell during the trial, doctor and patient will be unblinded earlier if necessary.

Patients taking part in a clinical trial will always be informed if it may involve use of a placebo.