Improving Breast Cancer Screening Uptake Through Tailored Reminder Letters (ENTER)

Equity in Breast Cancer Screening in Flanders: the Necessity of Tailored Reminders for Women With Low Socioeconomic Status

The goal of this trial is to learn whether a culturally and linguistically tailored reminder letter can increase participation in the Flemish Breast Cancer Screening Program among women who previously did not attend screening. The study also examines whether the effect differs between socioeconomic groups.

The main questions it aims to answer are:

• Does a tailored reminder letter increase participation among previous non-attenders?
• Does the effect differ between women with lower and higher socioeconomic status?

Researchers compare two groups:

• Intervention group: receive the standard invitation letter plus an additional tailored reminder letter.
• Control group: receive the standard invitation letter only.

Participation in screening within 40 days of the invitation is measured using the program's registry.

Participants are women aged 50-69 years who had previously been invited but had never attended screening. The reminder letter is sent as part of routine screening communication, and no additional medical procedures are involved.

Study Overview

• Status: Completed
• Conditions: Health Behavior; Breast Cancer Screening; Mammography
• Intervention / Treatment: Behavioral: Tailored reminder letter

Detailed Description

This study aims to evaluate the effectiveness of a culturally and linguistically tailored reminder letter in increasing mammography uptake within the Flemish Breast Cancer Screening Program (BCSP) among women who previously did not attend screening. The objectives are to:

• Quantify the difference in uptake between the intervention and control arms; and
• Assess whether the effect differs according to socioeconomic status (SES).

Study Setting:

The study is embedded within the Flemish BCSP, which is coordinated by the Centre for Cancer Detection (CvKO). The BCSP provides biennial screening mammography, free of charge, to eligible individuals aged 50-69 years registered as female in the Belgian national registry. Recruitment occurs through the routine program invitation process, where eligible individuals receive a mailed invitation letter indicating the time and location of their screening appointment.

Study design:

This study is a two-arm, parallel-group, superiority, randomized controlled trial (RCT) with partial blinding.

Study arms:

• Intervention arm: Participants allocated to the intervention arm receive two mailed communications: (1) the standard BCSP invitation letter, and (2) a tailored reminder letter, specifically designed to address linguistic and cultural barriers that may affect screening participation.
• Control arm: Participants allocated to the control arm receive the standard BCSP invitation letter only.

Detailed descriptions of study Arms and Intervention, Study Design (Masking, Allocation), Outcome Measures and Eligibility are provided in the designated sections.

Statistical analysis:

The primary analysis compares BC screening uptake between the intervention and control arms in the overall study population. The effect of the intervention is quantified using odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Statistical significance is assessed using the likelihood-ratio chi-square test (x²), with two-sided p-value < 0.05. Stratified analyses are conducted by socioeconomic status (SES), age group, province of residence, and type of mammographic unit. Analyses are performed according to both intention-to-treat (ITT) and per-protocol (PP) principles, with ITT as the primary analytic approach and PP as a sensitivity analysis. The ITT population comprises all randomized participants, excluding records removed before analysis during routine quality control procedures (e.g., duplicate system entries or invalid identifiers). The PP population comprises participants who receive the allocated intervention as planned and for whom complete outcome data is available. Exclusion criteria for the PP analysis comprise withdrawal or opt-out from the BCSP prior to receipt of the assigned communication strategy and documented logistical issues affecting letters delivery in either study arm. Deaths or emigrations occurring prior to participation are not specifically addressed in the PP definition as they are assumed to be evenly distributed between study arms, in line with routine cross-checks with demographic registries. No multivariable adjusted analyses are performed. Stratified analyses are interpreted descriptively, and no formal correction for multiple comparisons is applied.

• Study Type: Interventional
• Enrollment (Actual): 7947
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Belgium
  • Antwerp, Belgium, 2000
    • University of Antwerp
  • Bruges, Belgium
    • Centre for Cancer Detection (CvKO)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria

Individual-level criteria:

• Aged 50-69 years
• Legally registered as female in the Belgian national population registry
• No history of breast cancer in the previous 10 years
• No bilateral mastectomy in the previous 10 years
• Invited for mammography between April and June 2024
• Classified as a non-attender, defined as (1) having received at least one previous screening invitation, and (2) never having participated in the screening program.

Area-level criteria:

To increase the inclusion of socioeconomically vulnerable individuals while maintaining representation from the broader screening population, participants are selected from the list of individuals invited at mammographic units located in municipalities with high deprivation scores, defined as meeting at least two of the following criteria:

• Average income per capita < EUR 20,000
• Belgian Multiple Index of Deprivation score < 6
• Proportion of residents eligible for increased reimbursement for medical expenses > 12%.

Exclusion Criteria

• Actively opted out of the screening program at the time of the study
• Invited for screening in the previous year
• Underwent mammographic screening in the previous year

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Screening
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Tailored reminder letter; Participants allocated to the intervention arm receive two mailed communications: (1) the standard Breast Cancer Screening Program invitation letter, sent approximately three weeks before the scheduled screening appointment (±4 days); (2) an additional culturally and linguistically tailored reminder letter, sent approximately one week before the scheduled appointment (±4 days). The tailored reminder letter is specifically designed to address linguistic and cultural barriers that may affect screening participation.	Behavioral: Tailored reminder letter; The intervention development process is described in detail elsewhere (DOI: 10.1186/s13690-025-01591-7). A brief summary is provided below: The tailored reminder letter was developed using an iterative, participatory approach between April and October 2023. Three focus group discussions with 19 eligible women identified barriers to screening participation and limitations of the existing invitation letter. Based on these findings, a draft letter was refined through a Delphi process involving experts and stakeholders familiar with the screening program and target population. The letter was then improved during a co-creation session with 14 eligible women and validated through a final expert member check. The final reminder letter was designed for a low-literate audience, using simplified language and visual elements. It included essential appointment information and a QR code linking to translations in multiple languages to improve accessibility for linguistically diverse populations.
No Intervention: Standard of care; Participants allocated to the control arm receive the standard BCSP invitation letter only, approximately three weeks before the scheduled screening appointment (±4 days), with no additional reminder. The content of the standard invitation letter is publicly available on the website of the Centre for Cancer Detection (CvKO).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Screening uptake	Screening uptake, defined as the proportion of invited individuals who attend a mammographic appointment within the pre-specified time frame.	Within 40 days after invitation letter is sent.

Collaborators and Investigators

• Sponsor: Universiteit Antwerpen
• Collaborators: Thomas More University of Applied Sciences; Stichting tegen Kanker; Intermutualistic Agency; Centre for Cancer Detection (CvKO)
• Investigators: Study Chair: Guido Van Hal, Universiteit Antwerpen

Publications and helpful links

General Publications

• Ferrari A, Van Bos L, Talboom S, van de Veerdonk W, D'haenens W, Pak M, Descan M, Parmentier S, Van Collie L, Sibiet P, Goossens M, Van Hal G. From barriers to participation: co-creating an effective reminder letter for breast cancer screening among underserved women in Flanders. Arch Public Health. 2025 May 14;83(1):132. doi: 10.1186/s13690-025-01591-7.
• Ferrari A, Jael Herrera D, Van De Veerdonk W, D'haenens W, Ruiz Alejos A, Yimer NB, Orwa S, Van Bos L, Talboom S, Ding L, Goossens M, Van Hal G. Advancing Mammographic Screening Among Underserved Groups: A Systematic Review and Meta-Analysis of Intervention Strategies to Increase Breast Cancer Screening Uptake. Public Health Rev. 2025 Apr 4;46:1607873. doi: 10.3389/phrs.2025.1607873. eCollection 2025.

Helpful Links

• Information Security Committee Deliberation n. 25/044 (01/04/2025) regarding the linking of pseudonimized health insurance data from the intermutualistic Agency to mammography data from the Centre for Cancer Detection in the context of the ENTER study.

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2024
• Primary Completion (Actual): September 30, 2024
• Study Completion (Actual): December 16, 2025

Study Registration Dates

• First Submitted: February 17, 2026
• First Submitted That Met QC Criteria: March 11, 2026
• First Posted (Actual): March 16, 2026

Study Record Updates

• Last Update Posted (Actual): March 16, 2026
• Last Update Submitted That Met QC Criteria: March 11, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Randomized controlled trial; Breast cancer; Breast cancer screening; Reminder; Health equity; Reminder letter
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Behavior; Skin and Connective Tissue Diseases; Breast Neoplasms; Health Behavior
• Other Study ID Numbers: CPR-2022/1888

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The study protocol is made publicly available. Aggregated study results may be shared upon reasonable request. Individual participant data are derived from screening and health insurance registries and are subject to Belgian data protection regulations, requiring specific authorization from the competent authorities.
• IPD Sharing Time Frame: The study protocol will be publicly available following publication of the primary results. Aggregated data may be shared upon reasonable request after publication.
• IPD Sharing Access Criteria: Aggregated data may be shared with researchers for scientific purposes upon reasonable request to the study investigators. Requests involving individual-level data must comply with Belgian regulations and require prior authorization from the competent data protection authorities [e.g., Institutional Review Board, Information Security Committee (ISC)].
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No