Understanding the reasons for declining to participate in cancer genetics and genomic studies in the United States: A scoping review

INTRODUCTION: Cancer is the second leading cause of death in the United States (US). Genetics and genomic cancer studies have improved understanding of risk, onset, progression, and have informed treatment options. However, many populations are underrepresented in existing studies, and reasons why some individuals decline to participate remain unclear. To address this gap, we conducted a scoping review to summarize the reasons associated with declining participation in cancer genetics and genomic studies among cancer patients in the US. METHODS: A standardized search strategy was developed and deployed in Medline (PubMed), Embase (Ovid), and Scopus from database inception until March 13th, 2025. The search covered three concepts: cancer, genetics and genomic research, and declination to participate. A two-step screening process ensued against predefined inclusion criteria. Study characteristics were summarized descriptively. Reported reasons were harmonized into common data elements (CDEs). A network analysis was conducted to evaluate co-occurrence of CDEs and identify barriers. Recommendations to address barriers were mapped to specific themes and discussed with community members during the PE-CGS annual meeting. RESULTS: A total of 18,114 studies were imported, after the selection process, 19 studies were included in the review. Most studies were cross-sectional (42%), published after 2019 (58%), and reported on clinical genetic testing (58%). The most evaluated cancer sites were breast (n=13), ovary (n=9), and colon-rectum (n=7). The mean declination rate was 22.7% (SD=5.3). Non-Hispanic White, non-Hispanic Black, and Asian individuals reported lower declination rates than the mean, while Hispanic/Latino/a/x, American Indian/Alaska Native, and Native Hawaiian or other Pacific Islander individuals had higher rates of decline (27-28%). Network analysis showed that financial concerns with emotional distress or low perceived utility often co-occurred. Physical or medical limitations and sample collection issues were common reasons for declining genetic testing, and financial or insurance concerns and low perceived relevance were more frequent in testing done to guide clinical decision-making only. Three overarching barriers were identified: behavioral, logistical, and structural. Educational interventions, flexible participation strategies, and system-level improvements are key recommendations, endorsed by community members with whom we discussed results. CONCLUSION: Declining participation arises from behavioral, logistical, and structural barriers. Emotional, financial, and perceived utility concerns were most common and interrelated. Tailored education, provider engagement, and improved system accessibility may enhance equitable participation in cancer genetics and genomic studies.