Key Terms Associated with Clinical Trial Phases

The following terms are often used in discussions of a clinical trial and its phases.

  • Accrual –  The process of enrolling patients in a clinical trial, or the number of patients already enrolled or anticipated to be enrolled in a clinical trial.
  • Arm – One of the treatment groups of a randomized trial. The majority of randomized trials have two, but some have more.
  • Cohort – A group of patients in the same study receiving the same treatment or placebo.
  • Control group – The arm of a randomized clinical trial that gets the standard treatment or placebo (no treatment).
  • Double-blind – Aspect of a randomized trial in which neither the participant nor the investigator knows the arm of the trial to which the patient is assigned. The purpose is to eliminate any bias in the reporting of results.
  • Endpoint – The goal of the trial; what a clinical trial is trying to measure or find out. Typical endpoints include measurements of toxicity, response rate, and survival.
  • Experimental group – The arm of a randomized trial that gets the new treatment.
  • Maximum-tolerated dose (MTD) – The highest dose of a treatment that most people can safely withstand.
  • Placebo – An inert (inactive) substance often used in clinical trials for comparison with an experimental drug. No clinical trial for cancer patients in the U.S. can ethically or legally randomize patients to receive a placebo alone when they require treatment. In the placebo arm of a cancer treatment trial, patients receive treatment with approved therapy plus a placebo.
  • Progression-free survival (PFS) – The length of time during and after the treatment of myeloma that a patient lives with the disease but the myeloma does not get worse. In a clinical trial, PFS is one way to measure how well the treatment is working.
  • Progressive disease –  Myeloma that is becoming worse or relapsing, as documented by tests. Defined as an increase of ≥ 25% from the lowest confirmed response value in the myeloma protein level and/or new evidence of disease.
  • Randomized clinical trial – A research study in which subjects are randomly assigned to receive a particular treatment or not.
  • Refractory –  Disease that is no longer responsive to standard treatments. Myeloma is refractory in patients who have had progressive disease either during treatment or within 60 days following treatment. Most clinical trials for advanced disease are for patients with relapsed and/or refractory myeloma.


The International Myeloma Foundation medical and editorial content team

Comprised of leading medical researchers, hematologists, oncologists, oncology-certified nurses, medical editors, and medical journalists, our team has extensive knowledge of the multiple myeloma treatment and care landscape.

Additionally, the content on this page is medically reviewed by myeloma physicians and healthcare professionals.

Last Medical Review:  May 24, 2024 

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