A Tailored Reminder Letter Boosts Breast Cancer Screening and Narrows the Equity Gap

A simple letter, rewritten with the help of the very women it was meant to reach, has done something that many expensive public health campaigns fail to achieve: it persuaded thousands of women who had ignored repeated invitations to finally attend a mammogram, and it did so most powerfully among those living closest to the poverty line. A randomized controlled trial conducted in Flanders, Belgium, and published in the International Journal for Equity in Health, shows that a culturally and linguistically tailored reminder letter nearly doubled screening participation among women who had previously not responded to standard invitations, with the largest gains concentrated in low socioeconomic status groups. The findings offer a strikingly low-cost template for health systems everywhere that struggle to make population-based screening programs work for everyone, not just for the well-off.

Organized breast cancer screening is one of the quiet success stories of modern public health. By inviting women in a target age group to attend mammography at regular intervals, organized programs detect tumors earlier than opportunistic screening, and earlier detection translates directly into better treatment outcomes and reduced breast cancer specific mortality. In Flanders, the regional Breast Cancer Screening Program has been associated with substantial reductions in deaths from the disease among women who participate. Yet the program has a persistent Achilles heel: participation remains suboptimal overall, and it follows a steep social gradient. In neighborhoods where average income hovers around the poverty line, participation rates fall below 40 percent, meaning that the women who could benefit most from early detection are precisely the ones least likely to be screened.

This pattern, in which preventive services reach the advantaged first and most, is one of the most stubborn mechanisms by which health inequities reproduce themselves. Women with lower incomes, lower educational attainment, or migration backgrounds may face practical barriers such as inflexible work schedules, childcare responsibilities, or unstable housing, but they also face informational and cultural barriers: invitation letters written in formal administrative language, health literacy demands that assume familiarity with screening concepts, and materials that never reflect the lives or languages of the readers. The research team, led by Allegra Ferrari of the University of Antwerp together with colleagues at the Center for Cancer Detection in Bruges and partner institutions, set out to test whether redesigning a single piece of communication could begin to dismantle those barriers.

The intervention itself was deliberately co-created rather than imposed. The tailored reminder letter was developed together with women of low socioeconomic status and with experts from sector organizations, including community health workers and groups supporting migrant and disadvantaged communities such as Solidaris, FMDO, Saamo, and others. This participatory design process matters scientifically as well as ethically: materials written by professionals for a hypothetical audience often miss the actual sticking points, whether those are distrust of institutions, confusion about what a mammogram involves, or simply a letter that reads like a bill rather than an invitation. By grounding the wording, tone, and structure in the lived experience of non-attenders, the team aimed to produce a reminder that felt personal, understandable, and actionable.

To evaluate the letter rigorously, the researchers ran a two-arm, parallel-group, superiority randomized controlled trial between April and June 2024. The study population consisted of women who had not responded to the standard screening invitation, the so-called non-attenders, a group in which conventional outreach typically underperforms. In total, 7,922 non-attenders were randomized in a one-to-one ratio. The control group received the standard invitation alone, while the intervention group received the standard invitation plus the tailored reminder letter. The primary outcome was attendance at screening within 40 days, a window chosen to capture the immediate behavioral response to the mailing. Because participation data were drawn from screening and health insurance registries through secure data linkage performed by the InterMutualistic Agency, the outcome measurement was objective and complete, immune to the recall and self-selection biases that plague survey-based studies.

The results were unambiguous. Overall, 997 women, or 12.6 percent of the study population, attended screening within 40 days. Participation was substantially higher in the intervention arm, at 15.8 percent, than in the control arm, at 9.4 percent, an absolute difference of 6.4 percentage points corresponding to an odds ratio of 1.81 with a 95 percent confidence interval of 1.58 to 2.07. In plain terms, a woman who received the tailored reminder had roughly 81 percent higher odds of attending screening within the window than an otherwise identical woman who received only the standard invitation. For a static intervention, a letter added to an existing centralized mailing system, that effect size is remarkable, and the statistical precision of the estimate leaves little doubt that the difference was driven by the intervention rather than by chance.

The most consequential finding, however, emerged when the researchers stratified the analysis by socioeconomic status. About 27 percent of participants were classified as low-SES. Among these women, the tailored reminder tripled participation, raising attendance from 4.0 percent in the control group to 12.0 percent in the intervention group, an absolute gain of 8 percentage points and an odds ratio of 3.24 with a 95 percent confidence interval of 2.27 to 4.61. Among women who were not classified as low-SES, the effect was more modest, lifting participation from 11.7 percent to 16.9 percent, an absolute gain of 5.2 percentage points and an odds ratio of 1.53. Because the intervention worked more strongly for the disadvantaged group, it did not merely raise overall participation; it actively narrowed the socioeconomic gap in screening, compressing a participation difference of nearly 8 percentage points at baseline to roughly 5 percentage points after the reminder.

This equity-narrowing property is what distinguishes the trial from the many studies that show reminders can nudge attendance. Interventions that raise participation uniformly, or that work better among the advantaged, tend to widen absolute disparities even as they improve population averages, a phenomenon sometimes described as intervention-generated inequality. Here the opposite occurred, and the mechanism is plausible: the letter was designed specifically to address the barriers faced by women of low socioeconomic status, so it functioned as what epidemiologists call a proportionate universalism-style intervention, universal in delivery but calibrated in content to those with the greatest need. The trial was registered at ClinicalTrials.gov as NCT07472036, and the protocol received ethics approval from the University of Antwerp together with formal endorsement from the Flemish Working Group on Breast Cancer Screening. Because the reminder was embedded in routine screening communications and involved only a minor modification to the standard invitation scheme, individual informed consent was not required, and no participant’s access to screening or usual care was affected.

The implications extend well beyond Flanders. Many countries with organized screening programs, from the Netherlands and the United Kingdom to Canada and Australia, rely on centralized invitation systems that mail standardized letters to eligible populations. Such systems are efficient but blind to the social heterogeneity of their recipients. The Belgian trial demonstrates that the marginal cost of adding a second, better-designed communication for non-responders is small, while the marginal benefit is concentrated exactly where public health needs it most. For program managers, the actionable lesson is procedural as much as technical: involve non-attenders and community organizations in drafting the message, test it in a randomized design rather than assuming it will work, and measure effects stratified by socioeconomic position so that equity impacts are visible rather than hidden in pooled averages.

Certain caveats deserve honest acknowledgment. The trial was registered retrospectively, which is a limitation in reporting rigor even though the randomized design and registry-based outcomes protect the main findings. The 40-day follow-up window captures immediate response but not whether the effect persists across screening rounds or whether reminded women return at the next invitation cycle. And a letter, however well crafted, cannot resolve structural barriers such as transport, childcare, or inflexible working hours that no amount of wording can overcome. Still, the core result stands as a persuasive proof of concept: communication designed with, rather than merely for, disadvantaged communities can measurably shift behavior and reduce inequity at population scale. As health systems confront the rising costs of late-stage cancer care, the humble reminder letter, co-written with the women it serves, may prove one of the best investments in the equity toolkit.

Subject of Research: Tailored reminder letters to reduce socioeconomic inequities in organized breast cancer screening participation

Article Title: Improving participation in breast cancer screening through a tailored reminder letter: a randomized controlled trial tackling socioeconomic inequities

Article References: Ferrari, A., Goossens, M., Van Bos, L., van de Veerdonk, W., Vandemaele, E., Vanhecke, J., Tran, T. N., Martens, P., Ding, L., de Bock, G. H., & Van Hal, G. (2026). Improving participation in breast cancer screening through a tailored reminder letter: a randomized controlled trial tackling socioeconomic inequities. International Journal for Equity in Health. https://doi.org/10.1186/s12939-026-03027-2

Image Credits: AI Generated

DOI: 10.1186/s12939-026-03027-2

Keywords: breast cancer screening, health equity, randomized controlled trial, reminder letter, health communication, socioeconomic status, mammography, population screening, Belgium, Flanders, cancer prevention, public health