Date Published: June 12, 2019
Publisher: Public Library of Science
Author(s): Felix G. Rebitschek, Nora Pashayan, Martin Widschwendter, Odette Wegwarth, Amanda Ewart Toland.
Personal cancer risk assessments enable stratified care, for example, offering preventive surgical measures such as risk-reducing mastectomy (RRM) to women at high risk for breast cancer. In scenario-based experiments, we investigated whether different benefit–harm ratios of RRM influence women’s consideration of this, whether this consideration is influenced by women’s perception of and desire to know their personal cancer risk, or by their intention to take a novel cancer risk-predictive test, and whether consideration varies across different countries.
In January 2017, 1,675 women 40 to 75 years of age from five European countries—Czech Republic, Germany, UK, Italy, and Sweden—took part in an online scenario-based experiment. Six different scenarios of hypothetical benefit–harm ratios of RRM were presented in accessible fact box formats: Baseline risk/risk reduction pairings were 20/16, 20/4, 10/8, 10/2, 5/4, and 5/1 out of 1,000 women dying from breast cancer.
Varying the baseline risk of dying from breast cancer and the extent of risk reduction influenced the decision to consider RRM for 23% of women. Decisions varied by country, risk perception, and the intention to take a cancer risk-predictive test. Women who expressed a stronger intention to take such a test were more likely to consider having RRM. The desire to know one’s risk of developing any female cancer in general moderated women’s decisions, whereas the specific desire to know the risk of breast cancer did not.
In this hypothetical scenario-based study, only for a minority of women did the change in benefit–harm ratio inform their consideration of RRM. Because this consideration is influenced by risk perception and the intention to learn one’s cancer risks via a cancer risk-predictive test, careful disclosure of different potential preventive measures and their benefit–harm ratios is necessary before testing for individual risk. Furthermore, information on risk testing should acknowledge country-specific sensitivities for benefit–harm ratios.
Genetic, epigenetic, lifestyle, and reproductive factors alone or combined can be used to predict a woman’s risk for developing breast cancer.[1–3] Although the average 10-year absolute risk of breast cancer in women in the UK aged 50 years is 2.85%, women at the lowest and highest percentile of the risk distribution have a 0.53% and 9.96% 10-year risk, respectively. Risk prediction can be used in each of these cases to enable risk-stratified early detection and risk-reducing preventive interventions.[5–7]
We developed an online survey questionnaire, which was translated into five languages. FORECEE Consortium members from each of the five countries checked for the correctness and completeness of the translation. The survey was administered via e-mail by the market research institute Harris Interactive (Germany) to a sample of the Harris Interactive Panel and the Toluna Panel (sampling frame details in S1 Text).
Among the 1,675 women in the study (the participants characteristics are described in S1 Table), we identified three general response patterns (Table 1): 968 (58%) did not consider mastectomy in any of the presented scenarios, 323 (19%) decided to consider mastectomy in each of the six scenarios, and 384 (23%) women varied their responses across the scenarios. Thus, only for the latter group does the numerical relationship between cancer risks and risk reduction through RRM appear to have an effect on their decisions to consider mastectomy. Notably, 112 out of 384 participants violated transitivity across scenarios at least once: 46 considered a mastectomy for reducing mortality risk from 20 to 12, but not for a reduction from 20 to 4 out of 1,000; 53 participants considered it for 10 to 6, but not for 10 to 2; and 41 participants considered it for 5 to 3, but not for 5 to 1.
Only 23% of the participants varied their decisions on RRM according to a given baseline risk of breast cancer mortality and the expected risk reduction due to the mastectomy. In contrast, most of the women always applied the same response strategy, that is, always responded “yes” or “no” regardless of information provided. Although this phenomenon may hint to the fact that the presented scenarios did not translate well to the women in our study, it is worth noting that the consistent response patterns systematically varied across the five European countries. For instance, we saw the largest proportion of women who would not consider undergoing RRM in Germany and the largest proportion who would always consider it in the United Kingdom and Sweden. Thus, the proportion of consistent response patterns observed in our survey might be less an artefact of women not understanding the information provided than a general national attitude toward having preventive surgeries to reduce cancer risk. The observed variations in our study are indeed quite in line with real uptake rates in different countries. In Wales (UK), 34% of all BRCA mutation carriers identified up to 2015 underwent RRM, and 40% of participants opted for bilateral RRM in a study in England. US data similarly indicate increasing acceptance of this preventive measure. A study from the Netherlands shows that 36% of BRCA mutation carriers chose to undergo RRM within five years after disclosure of the test result.