Hypothetical Willingness to Share the Genetic Test Results among the Relatives of Individuals with HBOC: A Study on the Japanese Population

Objective: Hereditary breast and ovarian cancer syndrome (HBOC) increases the risk of developing breast, ovarian, prostate, and pancreatic cancers. With the insurance coverage for BRCA genetic testing, the number of individuals diagnosed with HBOC has increased. To use these test results effectively, cascade genetic testing (CGT) is recommended for at-risk relatives; however, it is not yet widely available. The purpose of this study was to investigate the willingness of the general population to share genetic test results and undergo CGT, as well as to analyze the factors influencing these decisions. Based on these findings, the study aimed to identify the types of support needed to support the sharing of genetic test results and promote the use of CGT. Methods: An online survey was conducted with 500 participants (50 men and women from each of the five generations, ranging from 20 to 69 years). Results: Among the HBOC blood relatives, 51.2% wanted to share the genetic results and 71.9% expressed a willingness to undergo CGT. “Matters to be shared with relatives” and “Helpful for my cancer prevention” were identified as key factors promoting the willingness to share the BRCA genetic test results and undergo CGT. The motivation for “Helpful for my cancer prevention” had a particularly strong influence on the decision to undergo CGT. Conclusion: In the general population, there is an emerging understanding that the genetic information impacts not only the individuals but also their entire families and can be valuable for cancer prevention. To promote the sharing of BRCA genetic test results and CGT uptake, the healthcare providers should offer support tailored to each family’s circumstances and establish cancer prevention measures recommended for HBOC.