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We hope these answers address any questions you might have about the AgeX trial.

Why is this research being done?

Women of ages about 50 to 70 in the UK are normally invited for breast screening every three years. While we know a lot about the effects breast screening has for women between these ages, there is not enough evidence on the effects for women aged somewhat less than 50 or somewhat over 70.

What is the purpose of this trial?

This trial will assess the risks of offering an additional screen (in particular, the chances of being diagnosed and treated for a non-life-threatening cancer) and benefits (in particular, the chances of saving life) for women slightly younger than 50 and, separately, for women slightly older than 70.

Who is participating in the trial?

Women may be included in the trial if, between 2009 to 2020, they were aged 47-49 or 71-73 and lived in an area of England covered by one of the 70 breast screening centres involved in the trial.  

Who was offered an additional screen?

In each participating breast screening centre, about half the women aged 47 to 49 and half the women aged 71 to 73 were invited to screening. This was done by allocating groups of women (clusters) at random, like tossing a coin, either for the whole group to be offered an additional screen, or for the whole group not to be offered and additional screen.

How is information about trial participants obtained?

The NHS Breast Screening Programme provides the study team with information on all women regardless of whether or not they were offered additional screening. This information includes personal identifiers, such as name, data of birth and NHS number, needed for electronic record linkage to routinely collected health records held by NHS England.

The study team provides the personal identifiers to NHS England, and NHS England uses them to link to their records and return linked health data to the trial. Linked data include screening history data, hospital admission data, cancer registrations, and data on women who have passed away.

How is information about trial participants private and secure?

The linked data provided to the study team are stored securely at Oxford Population Health (the Nuffield Department of Population Health) in accordance with the Data Protection Act 2018 and with the procedures and policies of the University of Oxford.  

Once provided, the linked data are de-identified so the researchers using them cannot identify any individual. No direct contact with trial participants will be made by the research team.

More information is available in the privacy notice. 


It will take some time to get reliable information about the risks of offering an additional screen (in particular, the chances of being diagnosed and treated for a non-life-threatening cancer) and benefits (in particular, the chances of saving life).  The first report on risks is scheduled to be in 2025/2026 and the first report on benefits is scheduled to be in 2027/2008.   The reports will be published in academic journals, on this website, and through relevant media.

Who is organising the trial?

A team at the University of Oxford acts as the coordinating centre for the trial.

Can participants opt out if they do not wish to be part of the trial?

Participants who wish to opt out of the trial should write, stating “OPT-OUT” and their name, address and date of birth to: AgeX Trial Co-ordinating Centre, Cancer Epidemiology Unit, Richard Doll Building, Oxford OX3 7LF. This will in no way affect their screening or any treatment they receive.

What approvals have been obtained for the trial?

Ethical approval for the trial was granted in 2010 and again in 2016 from Ealing & West London (now Harrow) Research Ethics Committee (ref:10/H0710/9).

Please note the trial has approval to use participants’ data without their consent under Section 251 of the NHS Act 2006. This was approved by the National Information Governance Board Ethics & Confidentiality Committee and is reviewed annually by the Confidentiality Advisory Group (ref: ECC 1-04 (b)/2010).