Why is ethnicity important in hereditary cancer testing and how do founder populations impact testing strategies?

• A. Ethnicity has no impact; only family history matters
• B. Founders lower testing accuracy
• C. Ethnicity informs likelihood of founder mutations and can guide targeted panels
• D. Ethnicity solely determines prognosis after cancer develops

Answer: (C)

Ethnicity informs the likelihood that someone carries a founder mutation, and that in turn guides how we test. In some populations, a small number of specific pathogenic variants are responsible for a large share of hereditary cancer risk because of the founder effect. That means people from those groups have a higher pre-test probability of carrying those variants.

Because of this, testing can be tailored to be more efficient: start with a targeted panel that screens for the common founder mutations in that population, which can yield faster, more cost-effective results and make cascade testing of relatives straightforward if a founder variant is found. If the targeted test is negative or if a family history suggests other risks, clinicians can expand to broader sequencing or a multi-gene panel to catch non-founder mutations.

Ethnicity is not the sole determinant of prognosis or of all genetic risk, and many individuals have admixture or rare variants outside well-known founder mutations. But using population-specific founder mutation information helps optimize testing strategy and improve detection where those founder variants are common.