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A family-based approach to cascade genetic testing in a pediatric cancer clinic: challenges in test uptake and utility

Clinical Genetics and Therapeutics
  • Primary Categories:
    • Genetic Counseling
  • Secondary Categories:
    • Genetic Counseling
Introduction:
Cascade genetic testing (CGT) is a critical component of genetic counseling visits and informs recurrence risk and etiology of the condition in the family. Non-syndromic cancer predisposition disorders (NS-CPD) are hereditary conditions characterized by absence of physical signs and symptoms prior to cancer onset. Due to the lack of standardized guidelines, clinics vary in approach to family testing. This study analyzed the uptake and utility of a family-based approach to cascade genetic testing in a pediatric cancer clinic serving an ethnically diverse population in Houston, TX.

Methods:
A retrospective chart review, using electronic medical records and patient charts, of patients diagnosed with the six most commonly seen NS-CPDs identified 106 families who had completed results disclosure visits. We collected data including the proband’s age, sex, race/ethnicity, parents’ preferred language, and use of interpreter during visit. Pedigrees and disclosure letters were used to assess the number of relatives of each proband along with testing decisions and outcomes for each relative. Chi squared tests were used to analyze each relative type’s rate of test uptake and assess proband factors associated with test uptake amongst relatives. We identified 106 pediatric probands' families with a diagnosis of Hereditary retinoblastoma, Li-Fraumeni syndrome, Familial adenomatous polyposis, Hereditary paraganglioma-pheochromocytoma, or Rhabdoid tumor predisposition syndrome. Rate of test uptake as well as utility in assessing recurrence risk was evaluated.

 

Results:
 From these 106 probands’ families, we identified 99 mothers, 97 fathers, 116 full siblings, and 53 half siblings who were living and recommended testing at the visit. Of these relatives, 42% had documentation of completed cascade testing within 24 months after the proband's result disclosure. Forty-one percent of mothers were tested in comparison to 26% of fathers and 70.6% of full siblings were tested compared to 13.2% of half siblings. Statistical analysis revealed that siblings were more likely to have completed testing than parents (p<0.001). Amongst parents, mothers were more likely to complete testing than fathers (p=0.03) and amongst siblings, full siblings were more likely to complete testing than half siblings (<0.001). Probands’ age being less than 4 years, parents’ preferred language being Spanish, and interpreter use during visit were factors associated with lower test uptake amongst siblings. The most frequently documented reason for lack of test uptake was that the relative lives outside USA (p=0.008) followed by lack of insurance. There were no instances of recurrence risk being impacted by suspected parental gonadal mosaicism due to recurrence of CPD in siblings.

Conclusion:
This study is the first of its kind to evaluate a family-based approach to CGT in pediatric NS-CPDs. It adds to knowledge regarding the uptake of testing in first degree relatives of probands from a diverse and multicultural patient population. For genetic counselors, this information is critical to inform strategies to aid with completion of family testing, especially for patients from diverse backgrounds. Specifically, an increased need for clear communication, educational aids, and translated written material in the family’s native language can be considered in clinics serving diverse populations. This study will inform implementation of standardized methods for cascade testing in clinics serving ethnically diverse or underserved populations and reduce barriers to completion of family testing for NS-CPDs.

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