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Research and new methods

Phase III: is it better than standard care?

Phase III trials compare a new treatment with current standard treatment in large numbers of people. This is where it becomes clear whether the new treatment is truly better or safer.

Last updated: ~1 min read
Patients and a nurse sitting in a hospital corridor
Figure 1.Phase III: many participants in many hospitals

01Short answer

Hundreds to thousands of people take part, often in many countries and clinics. Participants are usually assigned by chance (randomisation): one group receives standard care and the other the new treatment. Outcomes such as survival, lasting remission, side effects and quality of life are followed for years. An independent committee checks the data regularly and can stop the trial early if clear benefit or harm appears. A positive phase III often leads to approval and a new standard.

02Simple explanation

Compared with standard care.

Many participants.

Randomisation.

The basis for approval.

03Scientific explanation

NCI: phase III trials test whether a new treatment is better than standard treatment.

NCI: new treatments are tested step by step, from the laboratory to clinical trials; only those proven safe and beneficial become standard care.

04What happens in the body?

Data monitoring committee

Experts who independently oversee the trial.

A network of clinics
Figure 2.A network of clinics.

Overall survival

One of the most reliable outcome measures.

Scales
Figure 3.Scales — Phase III: is it better than standard care?

How to read the news

Research news brings hope, but not every advance suits everyone. Look at who it was tested in, at what phase and in how many people.

Talk to your doctor

Show your doctor what you have read; they will explain how it relates to your diagnosis and treatment. Do not change your treatment on your own.

05From research news to a conversation: four steps

Read, check, ask, decide together.

Read — From a trusted source.1ReadFrom a trusted source.
Check — Phase, participants, result.2CheckPhase, participants, result.
Ask — Show your doctor.3AskShow your doctor.
Decide — Together, without rushing.4DecideTogether, without rushing.
SourceA trusted site.
DoctorA personal explanation.
SafetyNot changing treatment yourself.

06Key points at a glance

TopicIn brief
Data monitoring committeeExperts who independently oversee the trial.
Overall survivalOne of the most reliable outcome measures.
How to read the newsResearch news brings hope, but not every advance suits everyone. Look at who it was tested in, at what phase and in how many people.
Talk to your doctorShow your doctor what you have read; they will explain how it relates to your diagnosis and treatment. Do not change your treatment on your own.

07Key terms

Randomisation
Assigning people to groups by chance.
Overall survival
The share of participants alive after a set time.
Clinical trial
Testing a new treatment with volunteers.
Evidence
A result confirmed by reliable research.

08Key points

  • Compare.
  • Follow.
  • Decide.
  • Check the source.
  • Talk to your doctor.

09Frequently asked questions

If I get the old treatment in phase III, do I lose out?

Standard care is the best known treatment; whether the new one is better is not yet known.

When are results known?

Often years later.

Is this advance right for me?

Only your treating doctor can say, based on your diagnosis, stage and condition.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. If I get the old treatment in phase III, do I lose out?

  2. When are results known?

  3. Is this advance right for me?

My questions

12Sources

  1. National Cancer Institute. Phases of Clinical Trials
  2. National Cancer Institute. NCI Dictionary of Cancer Terms: phase III clinical trial
  3. National Cancer Institute. What Are Clinical Trials?
  4. National Cancer Institute. Using Trusted Resources
  5. National Cancer Institute. NCI Dictionary of Cancer Terms: genomic profiling
  6. National Cancer Institute. NCI Dictionary of Cancer Terms: liquid biopsy
  7. National Cancer Institute. NCI Dictionary of Cancer Terms: drug resistance
  8. National Cancer Institute. NCI Dictionary of Cancer Terms: menin inhibitor
  9. National Cancer Institute. NCI Dictionary of Cancer Terms: antibody-drug conjugate
  10. National Cancer Institute. NCI Dictionary of Cancer Terms: bispecific antibody
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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