What would I do? Perspectives on the factors underlying Lynch syndrome genetic testing and results sharing decisions for high-risk colorectal cancer patients.

Objective: Universal tumour testing for Lynch syndrome (LS) in all incident colorectal cancers (CRCs) and sequential diagnostic genetic testing is cost-effective in Australia. Because of this, our study aimed to understand factors underlying possible decisions faced by tumour test-positive CRC patients and their at-risk relatives throughout the LS diagnosis pathway.

Methods: Semi-structured telephone interviews were conducted with 23 participants, using four hypothetical scenarios. Vignette-guided closed- and open-ended questions asked about LS genetic testing uptake, discussing diagnosis with at-risk relatives, and risk-reducing interventions. Personal perspectives on genetic testing were collected pre-post vignette discussion. Inductive thematic analysis was performed on open-ended questions. Decisional pathway diagrams were developed to convey factors influencing complex decision-making processes.

Results: Participant responses incorporated unfolding scenario information, resulting in three decision themes: (1) wanting to know one's LS status; (2) informing family about LS; (3) navigating risk-reducing interventions. Across all themes, 'knowledge' emerged as a facilitator, and 'negative emotional experience' as a barrier. Personal supportive views toward genetic testing increased post-interview.

Conclusions: When communicating with tumour test-positive CRC patients or their relatives about LS genetic testing, providing guidance/resources to inform decisions around risk-reducing interventions and informing family members is critical. Scenario-driven interviews provide insight into what individuals might do when facing complex healthcare decisions and could aid informed decision-making. This approach may be applicable in other conditions, particularly with mainstreaming being increasingly introduced into the genetic context.