Factors associated with participation in a population-based feasibility study of risk-based prostate cancer screening in Estonia
Authors: Mari-Liis Väli, Reeli Hallik, Kaire Innos

Background: Prostate cancer is the second most common cancer among men and the fifth leading cause of deaths worldwide. Prostate cancer incidence in Estonia is among the highest in Europe. The European Commission has encouraged Member States to explore the feasibility of risk-based prostate cancer screening among men aged 50–69 years.
Objectives: To examine factors associated with participation in risk-based prostate cancer screening with special emphasis on invitation method, age, education, marital status, and native language. In addition, we aimed to describe participants’ feedback on the organisation of the screening process.
Methods: The study applied the risk-based screening algorithm developed by the PRAISE-U consortium, including prostate-specific antigen (PSA) testing, risk estimation by a urologist, MRT imaging and precision biopsy.
We invited 12,000 men aged 50–69, living in two large cities in Estonia who had valid health insurance, no history of prostate cancer and no PSA test within the past 12 months, to participate in the study. Men were randomized into three equal groups who received the invitation either by regular mail, email or SMS. Non-attenders in all groups received an SMS reminder. Men were offered the possibility to book an appointment to give a blood sample via online booking system or by phone. In this analysis, participation was defined as providing a blood sample for PSA testing. To assess the effect of different factors on participation rate, Poisson regression with robust variance was used to calculate prevalence rate ratios (PRRs) with 95% confidence intervals (CI).
Results: The overall participation rate was 28%, but significantly higher among men aged 50–59 compared to age 60–69 (32% vs. 23%). Sending SMS reminders increased participation from 16% (pre-reminder) to 28%. Compared to regular mail + SMS reminder, adjusted PRR was 0.90  (95% CI 0.84–0.96) for e-mail + SMS and 0.80 (95% CI 0.74–0.85) for SMS+SMS. Older men were less likely to participate (adjusted PRR 0.74; 95% CI 0.67–0.81) for age 65–69 and 0.72; 95% CI 0.66-0.78 for age 60–64, compared with men aged 50–54). Compared with highly educated men, lower participation was seen for those with primary (adjusted PRR 0.44; 95% CI 0.36–0.54) and secondary education (0.71; 95% CI 0.67–0.75).
Men who were single or divorced were less likely to participate compared to married men (adjusted PRR 0.78; 95% CI 0.72-0.84 and 0.65; 95% CI 0.60-0.71, respectively). Overall, the participants provided highly positive feedback on the web-based organization of the screening process. A recent PSA test was reported as the main reason for not participating.
Conclusion: Combining either regular mail or email with SMS reminder was the most effective invitation strategy. The results support the initiation of risk-based screening at younger age when men have not yet started opportunistic screening, and the approach needs to be tailored to different social groups. These findings provide important input for planning the next steps of risk-based prostate cancer screening in Estonia and across Europe.