Abstract
IMPORTANCE: Suboptimal adherence to recommended surveillance mammography remains a challenge even in countries with organized screening programs. Scalable strategies to re-engage overdue repeat screeners are urgently needed. OBJECTIVE: To evaluate the effectiveness of pragmatic behavioral interventions in increasing mammogram uptake among overdue repeat screeners. DESIGN, SETTING, AND PARTICIPANTS: This 5-group randomized clinical trial was conducted from September to December 2024 in Singapore's integrated tertiary hospital system. Eligible participants were women aged 50 to 69 years who were overdue for a repeat screening (with ≥1 prior mammogram not conducted in the past 2 years), eligible for a free biennial screening as recommended for this age group, and registrants of the hospital's mobile health application. INTERVENTIONS: Participants were randomly allocated (2:1:1:1:1) into 5 groups: group 1 received personalized mailed reminder (MR); 2, MR plus US$7.50 conditional voucher; 3, MR plus conditional chance to win US$3750 lottery; 4, MR plus motivational videos; and 5, MR plus dedicated scheduling hotline. All groups also received 3 mobile-app push notification reminders, spaced 3 weeks apart. MAIN OUTCOMES AND MEASURES: Mammogram uptake in groups 2 through 5 compared to group 1 in 3 months. RESULTS: The analysis included 9000 women (median [IQR] age, 62 [58-66]) years. The 5872 (65.2%) who were aged 60 to 69 years had longer screening lapses (mean [SD], 7.7 [5.4] years) than those aged 50 to 59 years (mean [SD], 5.4 [3.5] years; P < .001). Mammogram uptake was 11.2% in group 1 and highest in group 5 (13.8%), but not significantly different. Groups 2 through 4 showed no significant increase over group 1. Participants who were more than 10 years overdue in groups 2 and 5 had slightly higher mammogram uptake (8.8%; relative risk [RR], 1.84; 95% CI, 1.13-3.00; and 8.9%; RR, 1.87; 95% CI, 1.14-3.07, compared to group 1 (4.8%), but not significant (P = .06 and .07, respectively). Engagement with digital interventions was low (<5% webpage views). Group 1 achieved a modest uptake relative to cost per additional mammogram, outperforming all other interventions in efficiency. CONCLUSIONS AND RELEVANCE: This randomized clinical trial found that a simple 1-time MR among overdue repeat screeners in Singapore's no-reminder, opt-in system may prompt repeat mammography, and additional behavioral interventions offered no incremental increase in mammogram uptake over MR alone. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT06733155.