Conclusion: Nearly one-third of at-risk relatives remain uninformed of their risk of carrying a cancer-associated pathogenic variant. Even among those informed, fewer than half subsequently complete genetic testing, representing a critical missed opportunity for precision cancer prevention.
Innovation: Five studies evaluating interventions to improve disclosure rates were generally ineffective. Urgent work is needed to elucidate barriers to relative disclosure by probands (a person serving as the starting point for the genetic study of a family) to develop targeted interventions that can optimize proband-mediated cascade genetic testing rates.