Considerations for hereditary breast and ovarian cancer syndrome molecular diagnosis: experience from the clinical practice.

Purpose: The implementation of the next-generation sequencing (NGS) in clinical practice has improved the genetic diagnosis of Hereditary Breast and Ovarian Cancer Syndrome (HBOC). We aimed to evaluate the diagnostic outcomes of using an NGS cancer gene panel in clinical practice for patients selected based on personal and/or family history of breast, ovarian, prostate, melanoma, and other HBOC-associated cancers.

Methods: The study series included 2561 consecutive Spanish individuals referred for genetic testing, comprising 2445 cancer patients and 116 healthy individuals with family history of HBOC. Eleven HBOC susceptibility genes (BRCA1, BRCA2, PALB2, ATM, CHEK2, BARD1, BRIP1, RAD51C, RAD51D, TP53, and PTEN) and three Lynch Syndrome genes (MLH1, MSH2, and MSH6) available for opportunistic testing were analyzed using a commercial Hereditary Cancer Panel and an in-house bioinformatics pipeline.

Results: Overall, the diagnostic yield was 11.0% in cancer patients and 8.6% in healthy individuals with a family history of breast/ovarian cancer. Pathogenic variants in high-risk genes were more frequent in patients with multiple HBOC tumors and a family history of different HBOC cancers. Additionally, we diagnosed five families with Lynch syndrome through opportunistic testing.

Conclusion: Testing cancer susceptibility genes using an agnostic strategy confers a diagnostic benefit for hereditary cancer syndromes compared to phenotype-driven test, without adding complexity to the study. The analysis of healthy individuals with a family history of HBOC detects pathogenic variants in a cost-efficient percentage of cases, resulting in a good alternative strategy when the index case is unavailable.