Uptake of Cascade Genetic Testing for Hereditary Breast Cancer in the Public Health System in a Middle-Income...

Hereditary breast cancer accounts for up to one-third of cases in Brazil. Cascade genetic testing is essential to identify at-risk relatives, yet uptake of cascade genetic testing remains low in most settings. This study aimed to evaluate referral and uptake of cascade genetic testing in a public university hospital using an indirect counseling approach.

We conducted an observational study including women followed at the High-Risk Clinic of CAISM/UNICAMP between 2021 and 2022. Probands carrying pathogenic or likely pathogenic (P/LP) variants were invited to refer up to 3 relatives for free cascade genetic testing through indirect counseling. Logistic regression analyses were performed to identify factors associated with family referral and test uptake.

Among 102 probands with P/LP variants, 48% referred at least one relative, totaling 186 invited. Of these, 161 completed testing (uptake: 86.6%). However, only 60.8% of the total tests available for cascade genetic testing were performed. A personal history of breast cancer in the proband was associated with a higher likelihood of family referral (odds ratio [OR] 2.52; 95% confidence interval [CI], 1.0-6.0). Among relatives, maternal history of breast cancer increased uptake (OR 5.80; 95% CI, 1.83-18.42), as did having a sister diagnosed with breast cancer (OR 3.86; 95% CI, 1.4-10.6).

Cascade genetic testing achieved high uptake in the Brazilian public health context, even when delivered through indirect counseling. Specific family cancer histories positively influenced uptake, underscoring the relevance of tailored genetic counseling strategies to strengthen testing implementation in middle-income countries.