ABSTRACT
Background/Objectives: Li-Fraumeni Syndrome (LFS) is a rare hereditary cancer predisposition syndrome characterized by high lifetime risks for multiple primary malignancies. Although most individuals with LFS inherit a pathogenic TP53 variant from a parent, approximately 20% have de novo variants with no suggestive family cancer history. This may result in an LFS experience distinct from individuals with affected relatives. This multi-case study report examines the unique psychosocial experiences of three young adults with de novo TP53 variants. Method(s): The National Cancer Institute's LFS study (NCT01443468) recruited adolescents and young adults (AYAs;aged 15-39 years) with LFS for qualitative interviews. Three participants had a de novo TP53 variant and a personal cancer history. An interprofessional team analyzed interview data using extended case study and narrative methods. Result(s): De novo participants lacked familiarity with LFS to situate a cancer diagnosis, interpret genetic test results, or adjust to chronic cancer risk. Communicating with and receiving support from family was challenged by their lack of common experience. De novo participants experienced socioemotional isolation, which was amplified during the COVID-19 pandemic. To cope, they sought support in online rare disease communities or through mental health providers. Conclusion(s): Individuals with de novo variants may lack familial guides and familiar providers to address disease management and uncertainty. Specialty health and mental health providers may support de novo patients across hereditary cancer syndromes by validating their uncertainties and connecting them with diseasespecific patient advocacy groups that support adjustment to chronic cancer risk.