Effects of a gift certificate incentive and specialized delivery on prostate cancer survivors' response rate to a mailed survey: A randomized-controlled trial

Abstract

Most men diagnosed with prostate cancer become long-term survivors, but are at risk for medical late-effects that can affect their long-term health. Mailed surveys are well suited to study late-effects in this population, but low response rates can compromise survey validity. This study investigated whether an unconditional $5.00 gift certificate incentive or Priority Mail delivery increased prostate cancer survivors' response to mailed surveys. 976 participants (mean age = 66.8 years), 2-8 years post-diagnosis, were randomized to one of four groups: Incentive; Priority Mail; Incentive & Priority Mail; or Control. After an introductory letter, initial study packets were mailed based on randomization; 46 days later, a second study packet was mailed to all non-responders by First-Class Mail. The first mailing yielded a significant variation in response rates across groups (χ(2) = 9.34; p = 0.025). Priority Mail (64.7%; p = 0.008) and Incentive & Priority Mail (63.6%; p = 0.016) groups had significantly higher response rates than Controls (52.9%). After the second mailing, the overall response rate increased significantly from 59.6% to 71.4% (p < 0.001); however, response rates no longer differed across groups (range, 69.3% [Incentive group] to 73.9% [Priority Mail group]). Long-term prostate cancer survivors' response rates to mailed surveys increased with the use of Priority Mail and a repeat survey mailing, but the unconditional gift certificate incentive was not supported in this population. By identifying and applying specialized survey methods, studies targeting survivors of prostate cancer and other geriatric cancers may improve response rates, thus limiting a source of potential bias.