Your Right to Stop at Any Time

Part of Understanding Cancer Trials: The people, your safety, and your rights.

About 4 minutes. Free, in your language, no account needed.

This is general education about clinical research — not medical advice, and not a way to join a study. Talk to your own doctor about your situation.

This is the single most important right in clinical research, and it is stated in international ethics guidance in plain terms.

The World Medical Association's Declaration of Helsinki, in its October 2024 version, states at paragraph 26 that a potential participant must be informed of the right to refuse to participate, or to withdraw consent to participate at any time, without reprisal.

What that means in practice

You may say no at the start, for any reason or for no reason.

You may say yes and then change your mind an hour later, a week later, or a year later.

You do not have to justify it. You do not need a medical reason. "I have changed my mind" is a complete answer, and no one is entitled to demand more.

Your care continues

This is the fear that stops people, so it should be said directly.

Stopping a study does not end your treatment, and it does not end your relationship with your care team. You return to the care you would otherwise have been receiving. Your team's obligation to you does not depend on your participation in research.

Nobody may treat you differently, delay your care, or be cold to you because you stopped. If that ever happened, it would be a serious failing, and the ethics committee contact on your consent documents exists partly for that reason.

What stopping actually involves

Tell the team. It does not have to be a formal letter — telling your research nurse or your doctor is enough to start the process.

Two things are usually offered, and both are reasonable to accept or decline.

A safety conversation. For some treatments there are medical reasons not to stop abruptly, or things to watch for afterwards. The team should explain this. That is medical information for your protection, not persuasion — and if it starts to feel like persuasion, you can say so.

Some final checks. The team may ask for a final visit or a follow-up contact to make sure you are well. You may agree to this or decline it.

Information already collected

One honest point that is often missed.

If you stop, information collected about you up to that moment usually stays in the study. It cannot generally be removed, because removing data from analyses that have already used it would distort the results and could make the study unreliable for everyone in it.

You can usually ask that no further information be collected about you, and you can usually separate the questions of stopping the treatment, stopping the visits, and stopping follow-up contact. What applies in your study, and in your country's data protection law, should be written in your consent documents, and you can ask for it to be explained.

Partial stopping

Stopping is not always all or nothing. Depending on the study, you may be able to:

• stop the study treatment but continue safety follow-up
• stop the extra research procedures but continue the treatment
• pause rather than stop
• decline an optional part, such as extra samples, while continuing the rest

Ask what the options are. They may be broader than a single yes or no.

In short

• You may refuse to take part, or stop at any time, without reprisal. This is stated in international research ethics.
• You do not have to give a reason.
• Your care and your relationship with your team continue. Nobody may treat you differently for stopping.
• Telling your research nurse or doctor is enough to start the process.
• Data already collected usually stays in the study, but you can usually stop further collection, and stopping is often not all or nothing.