Lottery ticket was more effective than a prize draw in increasing questionnaire response among cancer survivors

Compare the effect of financial incentives on response to a cancer survivors' postal questionnaire.

Prostate cancer survivors in Ireland, 1.5-18 years after diagnosis, were randomized to the (1) "lottery" arm [a € 1 lottery scratch card sent with the questionnaire (n = 2,413)] or (2) "prize" arm [entry into a draw on return of a completed questionnaire (n = 2,407)]. Impact of interventions on response overall and by survival period ("short term": < 5 years after diagnosis; "long term": ≥ 5 years after diagnosis) was compared as was cost-effectiveness.

Adjusted response rate was 54.4%. Response was higher among younger men (P < 0.001) and those with earlier stage disease (P = 0.002). A modest 2.6% higher response rate was observed in the lottery compared with the prize arm [multivariate relative risk (RR) = 1.06; 95% confidence interval (CI): 1.00, 1.11]. When stratified by survival period, higher response in the lottery arm was only observed among long-term survivors (multivariate RR = 1.10; 95% CI: 1.02, 1.19; short-term survivors: RR = 1.01; 95% CI: 0.94, 1.09). Costs per completed questionnaire were € 4.54 and € 3.57 for the lottery and prize arms, respectively. Compared with the prize arm, cost per additional questionnaire returned in the lottery arm was € 25.65.

Although more expensive, to optimize response to postal questionnaires among cancer survivors, researchers might consider inclusion of a lottery scratch card.