Mailed FIT-Based Outreach Interventions

CRC is the second most common cancer and cause of cancer-related mortality in Singapore. However, completion of CRC screenings remains suboptimal, with only 44.9% of eligible adults aged 50-74 years in Singapore up to date with CRC screening, far below the recommended 80% CRC screening completion rate set by the US Multi-Society Task Force on CRC. Singapore currently adopts a risk-stratified model for CRC screening, in which asymptomatic individuals without a family history of CRC are regarded as average-risk and are recommended annual fecal immunochemical test (FIT) or 5 to 10 yearly colonoscopies from 50 years old. However, these are usually recommended opportunistically by primary care providers during a routine healthcare visit. Among average-risk individuals, patients are more likely to participate in stool-based testing (34%-39%) than colonoscopy (24%-31%).

While FIT screening is cost-effective for health systems while reducing CRC mortality, the substantial screening gap underscores the need for interventions to increase FIT uptake. Numerous studies in other settings have compared the effectiveness of interventions such as mailed FIT, patient reminders, and patient navigation in improving screening uptake. Among these, mailed FIT outreach has emerged as a particularly effective strategy, reducing logistical barriers and enabling wider population coverage. Gupta et al. found that CRC screening participation was significantly higher for patients with mailed FIT (40.7%) compared to usual care (12.1%). A meta-analysis of randomized controlled trials (RCTs) by Ramal et al. found that patient navigation (RR, 1.58; 95% CI, 1.23-2.02) outperformed usual care in increasing CRC screening uptake. Meanwhile, a recent trial by Korostoff-Larsson et al. found that SMS reminders were associated with significantly improved FIT completion compared with usual telephone call reminders (58.9% vs 49.8%). The TEMPO trial by Robb et al. found that setting a 2-week deadline increased the FIT return rate compared with control (68.0% vs 63.2%). However, most of these studies compared single outreach interventions against usual care alone, leaving limited evidence on cost-effectiveness and on whether combining interventions produces synergistic, additive, or antagonistic effects. Therefore, it is important to assess the most effective and efficient strategy in the local context.

A successful FIT programme requires adherence to follow-up colonoscopy after an abnormal result. Large studies using data from community or national screening programs have shown colonoscopy completion rates of only 32%-56% within 1 year of an abnormal FIT/FOBT, and non-adherence to follow-up colonoscopy is associated with higher CRC incidence and mortality. A meta-analysis of 21 studies by our study team identified four interventions that increased completion of follow-up colonoscopy after an abnormal FIT: patient navigation (RR 1.24), patient reminders (RR 1.32), provider reminders (RR 1.36), and automated referral to gastrointestinal (GI) consult (RR 1.68).

Therefore, this study aims to identify the most effective and cost-effective strategy for increasing CRC screening participation and adherence within Singapore's public healthcare system. Specific objectives are to:

1. evaluate the effectiveness of mailed FIT outreach, reminders, patient navigation, and behavioural interventions in increasing initial FIT completion, sustained annual FIT adherence across three screening rounds, and reducing screening disparities;
2. assess the effectiveness of an evidence-based programme incorporating patient reminders, patient navigation, provider reminders, and automated gastroenterology referrals in increasing follow-up colonoscopy completion after abnormal FIT results;
3. evaluate whether improved screening participation and diagnostic follow-up increase the detection of early-stage CRC; and
4. evaluate the cost-effectiveness of competing intervention strategies from the healthcare system perspective.

This is a 3-year longitudinal screening trial consisting of 3 annual rounds of screening. Participants enrolled in Round 1 (Year 1) are intended to be followed for subsequent annual screenings (Year 2 and Year 3). Research funding and institutional approval are secured for Round 1; Rounds 2 and 3 are pending final funding approval.