The purpose of this study is to compare the uptake rates of a patient-initiated model of cascade testing with a registry-aided model amongst relatives of patients identified to have a particular cancer predisposition gene. Cascade testing allows the benefits of genetic testing to spread beyond the patient and enables other family members to make an informed choice on genetic testing. The researcher team hopes to study the rates of cascade testing using the two models, while concurrently comparing the adherence of identified carriers to risk management recommendations, including surveillance imaging and/or prophylactic surgeries. The team also aims to understand the willingness, acceptability and barriers of a registry-aided model.

Germline pathogenic/ likely pathogenic variants (PV/LPV) in cancer predisposition genes are defined as genetic alterations that increases an individual's susceptibility to cancer development. They are present in germ cells (egg or sperm) and can be passed down to subsequent generations.

Following the identification of a germline PV/LPV in a cancer predisposition gene in an index case presenting with disease (symptomatic proband), systematic cascade testing can be performed in relatives who have not yet developed disease (asymptomatic) to determine their future risk. Identifying asymptomatic carriers in families provides opportunities to ascertain hereditary risk, prevent disease via risk reduction surgery, diagnose disease in earlier stages, and ultimately improve clinical outcomes.

In spite of the evidence in support of cascade testing, there remain significant barriers to uptake that hinder the ability of a proband in Singapore to disseminate this critical information to his/her family.

The conventional approach to cascade testing in Singapore and most countries is to encourage probands with PV/LPV in cancer predisposition genes to relay this genetic information to their relatives and encourage them to see a genetic counsellor for discussion on predictive genetic testing. This proband-initiated disclosure is often suboptimal due to a myriad of reasons.

To improve the uptake rate of cascade testing in families at high risk of cancers, we propose a registry-aided outreach to family members of probands to bypass the barriers inherent with the proband-dependent approach. Our study shares the burden of communicating genetic results by having a healthcare professional reach out to family members and discuss the implications of germline cascade testing with at-risk relatives (ARRs). Alternative communication channels to reach out to relatives, independent of the proband, is thus created and propagated. This new model to enhance cascade testing features a two-pronged approach - personal communication by the proband, as well as a secondary registry-aided outreach to contact at-risk relatives.

This proposal is evaluated using a cluster randomized controlled trial to compare the effectiveness of the outreach program by comparing the cascade testing uptake rates between the current proband-dependent approach (control arm) and the combination of the proband-dependent approach with additional registry-aided testing reminders (experimental arm).

An in-depth interview with relatives who declined cascade testing will also be conducted to elucidate other barriers to cascade testing in the local population.

Inclusion Criteria:

Probands:

• Patients who undergo clinical genetic testing and seen at the Cancer Genetics Service (CGS) in National Cancer Centre Singapore
• Pathogenic variant/ likely pathogenic variant (PV/LPV) identified in a cancer predisposition gene
• Aged 21 years old and over
• Singapore citizen or permanent resident

ARRs:

• ARRs of a proband
• Aged 21 years old and over
• Singapore citizen or permanent resident

Exclusion Criteria:

• Lacks capacity to consent
• Not living in Singapore
• Probands who decline to share relatives' contact details
• Probands with no contactable relatives in Singapore