Breast cancer is the most common cancer in the United Kingdom, with 1 in 8 women affected during their lifetime. Whilst survival rates are high, the 5-year survival rate is 72% higher with the earliest stage breast cancer, compared to the latest disease stage. The National Health Service Breast Screening Programme invites women aged 50 to 70 years old every three years to a mammogram. By enabling earlier detection, it is estimated that the National Health Service Breast Screening Programme saves 1300 lives per year.

Despite the potential benefits of breast cancer screening, attendance is falling. Behavioural Science is a field of study concerning understanding the processes underpinning human action. Behavioural theories, such as the Capability Opportunity Motivation-Behaviour model. Recent studies have shown the application of behavioural science to screening may also facilitate uptake of invitations. However, the use of plain text messages limits which behavioural determinants can be feasibly addressed, and what techniques can be used. Video messages can allow for more complex and a broader range of behavioural change techniques to be incorporated, and therefore have greater impact upon attendance.

Whilst behavioural science-informed messages have previously been trialed by groups to facilitate breast screening attendance, their effectiveness has been variable. One of the reasons for this, is that text messages are of limited length and formatting capability, thus restricting the number of behavioural change techniques that can be included. Moreover, some behavioural techniques are more complex than others, and plain text can limit the extent to which these can be feasibly incorporated. Video messaging provides a delivery mechanism that may enable more complex, and different combinations to be trialed. There is however, a paucity of data regarding the impact of sending a video-based behavioural science message upon attendance rates at breast cancer screening programmes. This study looks to investigate the impact of a video-message, compared to behavioural science-based text messages and standard reminder messages.

The primary object is to determine the impact of behavioural science informed (1) video and (2) text messages compared to usual care, upon uptake of breast cancer screening. Secondary objectives involve how this impact on attendance differs between population subgroups including people from differing demographic groups.

This study will be conducted as a randomised control trial in the London screening region of the National Health Service Breast Screening Programme. The study will last over 6 months. The administrative hub for the National Health Service Breast Screening Programme. in London is based at the Royal Free Hospital, who will oversee invitation scheduling, message delivery and outcome data collation through their existing delivery systems.

Participants will be randomised using simple randomisation method in a 1:1:1 fashion to either intervention arm or usual care. Randomisation will utilise a computerised system in which each participant who is due for screening in the study period is randomly allocated a number corresponding to the message they will receive. This will be undertaken by the screening hub, and will be passed on to the message delivery service who will ensure the correct template is sent.

Written invitations are sent, as standard practice, by the National Health Service Breast Screening Programme. to invite women to either (1) an appointment at a set time, date and location (so-called timed invitations) or (2) to call and book an appointment (or open invitation). Following this, as part of usual care, those selected for open invitations will receive a first text message 7 days post written invitation. They will then receive two text message reminders, 7 days and 2 days prior to the appointment, once it has been booked. Those who receive timed invitations will just receive the two reminder messages, 7 and 2 days prior to the appointment. The decision to offer an individual a timed or open invitation is made by the screening service based on their pandemic recovery process, and will not be altered by this project.

This randomised controlled trial will involve randomising participants to receive the usual care messages (according to the timings outlined above), a plain text message incorporating or the behavioural message with a new link to a video incorporating more behavioural techniques.

The content of the intervention messages, and the video have been developed through extensive Patient and Public Involvement and Engagement work including 10 interviews, 2 focus groups and 2 co-design workshops. Members of the public have been consulted throughout the process, especially regarding the representations of individuals in the video, and the message content. The feedback received has been used to alter the materials, and further feedback received. Through this iterative approach we have ensured content is appropriate. We have also sought feedback from members of community groups working in mental health services specifically for African Caribbean and Arabic Speaking adults, and trans-led organisation to improve the quality of life of trans people, to ensure individuals from these groups are happy with representations. Screening commissioners at National Health Service England have also approved this content. The National Health Service Identity team have provided approvals for the use of National Health Service logos/branding, and the team at London Northwest Healthcare National Health Service Trust approved the use of their name.

The video will be hosted on a private page on the Imperial College London website, which will be available only to those who have been sent the link. The video will be translated into several languages, with voice overs also available in different languages, to ensure people from a diverse background are able to understand the content.

After 3 months from the initial written invitations, data will be collated from the breast screening hub regarding whether an individual attended an appointment and whether the messages were successfully sent. This will be repeated at 6 months corresponding to the key performance indicator of the service.

The inclusion criteria will match those used by the National Health Service Breast Screening Programme, as all invitations will come directly from the programme, as per usual care. These include:

• Aged between 50 to 70 at the time of invitation
• Lives within London screening region
• Registered as female with primary care physician

The exclusion criteria will match those used by the National Health Service Breast Screening Programme, as all invitations will come directly from the programme, as per usual care. These include:

• Previous attendance at breast screening in the current (3-year cycle)
• Opted out of receiving text messages
• Opted out of screening
• Previous bilateral mastectomy

Registered with primary care physician as female and therefore will be invited to the breast cancer screening programme

6 months

The screening services will not have access to the allocation of participants and will be masked. They will not be able to determine which messages are being sent to different women being invited to screen, as allocation will be undertaken by the third party messaging company following provision of a screening invitation list by the service.