Barriers and facilitators for medical oncologists in the further implementation of mainstream genetic testing in breast cancer care in the Netherlands

Only 67% of eligible patients with breast cancer currently undergo genetic testing. Mainstream genetic testing (i.e. healthcare professionals (HCPs) from outside the genetics field providing genetic counselling), also referred to asmainstreaming, leads to increased uptake of genetic testing. Unlike surgical oncologists, medical oncologists have not yet widely adopted mainstreaming. This study aims to identify barriers and facilitators for HCPs, in particular medical oncologists, in advancing the implementation of mainstreaming. Structured interviews were conducted with HCPs (predominantly medical oncologists) using the Constructive Technology Assessment (CTA) framework. Participants were recruited from all regions of the Netherlands, ensuring representation from academic medical centres, teaching hospitals and general hospitals. The interview data was analysed using thematic analysis. In this qualitative study, 12 medical oncologists, three nurse practitioners, three clinical geneticists, two clinical laboratory geneticists and one representative of a health insurer were interviewed. Lack of time and limited knowledge were the most commonly mentioned barriers, whilst effective cross-departmental collaboration and education were the most important facilitators. For medical oncologists specifically, financial compensation for the increased workload and the increasing importance of genetic testing for guiding therapy choices were found to be encouraging factors. This study identified several barriers and facilitators to mainstreaming being implemented by medical oncologists. Education to strengthen oncologists' skills in discussing germline genetic testing may address knowledge gaps and time barriers. Alongside cross-departmental collaboration, these strategies could streamline genetic testing pathways. Further research should evaluate their implementation and effects on patient experience and equitable access.