RISK COMMUNICATION IN THE DUTCH CANCER RISK TEST: THE MORE NUMBERS THE BETTER, OR NOT?

Purpose: The Cancer Risk Test provides personal information about the risk of cancer and ways to reduce this risk. The aim of the study is to determine whether quantification of the risks in the Dutch Cancer Risk Test affects users’ perception of cancer risks and to determine users’ evaluation of the Dutch Cancer Risk Test.

Method: Cross-sectional study using questionnaires. A total of 612 persons from the general population were given a shortened version of the test for colon and lung cancer submitted via the Internet. In total 12 different versions were tested that differed in the quantification of risks (i.e. quantification of population risk, and/or of calculated personal risk, and/or of relative risk reduction if changing lifestyle) and the addition of a population diagram (for population risk only). The standard version only provided risks in relative terms. Each participant received 1 version of the test for colon cancer and 1 version for lung cancer. Before and after going through the Cancer Risk Test participants were given a questionnaire.

Result: Going through the standard version of the Cancer Risk Test without quantified risk information improved understanding of the relative risk of cancer. Before 57% of the participants underestimated their personal risk of colorectal cancer and 38% their personal risk of lung cancer. The addition of quantitative information about the population risk to the standard version resulted in a doubling of the percentage of correct estimates of population risk and significantly improved the estimates of personal risk. It made no difference whether the population risk was only presented in numbers or if also a population diagram was presented. Quantitative representation of personal risks and risk reduction had no effect. Approximately 12% of participants indicated to have become more worried about the risk of cancer after undergoing the test. Participants judged largely positive about the Dutch Cancer Risk Test

Conclusion: Adding quantitative information about the population risk led to a better understanding of both the population risk as personal risk of cancer.