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Clinical Trial Terminology Defined

Randomized controlled trial – A research study in which patients are randomly assigned to a group to receive a particular treatment (either the new treatment or the standard of care). These trials may be “blinded” (the patient and the study physicians/researchers do not know which treatment the patient is receiving) or “open label” (the patient and the study physicians/researchers know which treatment the patient is receiving).

Arm – The specific treatment groups of a randomized controlled trial. The majority of randomized controlled trials have two arms, but some may have more.

Experimental arm – The group of patients in a clinical trial that is receiving the new treatment.

Control arm – The group of patients in a randomized controlled trial that gets the standard of care (or standard of care plus placebo). For example, if the current standard of care is “A+B”, and the new agent is being studied is “C”, people in the experimental arm receive “C” and people in the control arm receive “A+B”. In myeloma, the new agent is often studied in combination with the current standard of care. In that case, people in the experimental arm receive “A+B+C” and people in the control arm receive:

  • “A+B” if the trial is open label
  • ​“A+B + Placebo” if the trial is blinded

Cross-over option – In some clinical trial designs, there is a cross-over option for patients in the control arm. This means if a patient is receiving the standard of care treatment (A+B), but is no longer responding to treatment, they have the option to “cross-over” to the experimental arm and receive the new treatment (A+B+C).