← Back
Research and new methods

Scientific evidence: what can you trust?

Not all information is equally reliable. One person's story, a laboratory experiment and a large randomised trial are different levels of evidence.

Last updated: ~1 min read
Rows of books on library shelves in soft daylight
Figure 1.Not one study but a whole library

01Short answer

At the bottom of the evidence pyramid are individual stories and expert opinion; above them come cell and animal studies, then observational studies; at the top are well-run randomised trials and the systematic reviews that combine them. Clinical guidelines (NCCN, ESMO, ELN and others) gather the evidence and turn it into recommendations. A single study is rarely the last word; results need to be confirmed. "Miracle" claims need especially strong evidence.

02Simple explanation

Evidence has levels.

A story is not proof.

Replication matters.

Guidelines sum it up.

03Scientific explanation

NCI: reliable information is based on scientific evidence and reviewed by experts.

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?

Systematic review

A combined analysis of all studies on a topic.

Converging beams
Figure 2.Converging beams — Scientific evidence: what can you trust?

Clinical guideline

Official recommendations based on evidence.

A single light
Figure 3.A single light — Scientific evidence: what can you trust?

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
Systematic reviewA combined analysis of all studies on a topic.
Clinical guidelineOfficial recommendations based on evidence.
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

Level of evidence
How reliable the information is.
Meta-analysis
Statistically combining the results of several studies.
Clinical trial
Testing a new treatment with volunteers.
Evidence
A result confirmed by reliable research.

08Key points

  • Check the level.
  • Look for confirmation.
  • Ask about guidelines.
  • Check the source.
  • Talk to your doctor.

09Frequently asked questions

Someone I know says this remedy cured them.

That is a story, not evidence; talk to your doctor.

What evidence is my treatment based on?

Ask your doctor about the guidelines and trials.

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. Someone I know says this remedy cured them.

  2. What evidence is my treatment based on?

  3. Is this advance right for me?

My questions

12Sources

  1. National Cancer Institute. Using Trusted Resources
  2. MedlinePlus. Evaluating Health Information
  3. National Cancer Institute. What Are Clinical Trials?
  4. National Cancer Institute. Phases of Clinical Trials
  5. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: flow cytometry
  6. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: next-generation sequencing
  7. National Cancer Institute (NCI). Find NCI-Supported Clinical Trials
  8. U.S. National Library of Medicine. ClinicalTrials.gov
  9. Deutsches Krebsforschungszentrum. Krebsinformationsdienst
  10. KWF / NFK / IKNL. Kanker.nl
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
Last updated: ← Back to the list

Open the interactive site →