GTS5:BRCA-related cancer predisposition syndrome (BRCA1, BRCA2): Difference between revisions
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'''Tumor testing:''' Tumor sequencing may identify somatic ''BRCA1/BRCA2'' alterations, loss of heterozygosity, or reversion mutations, which have implications for therapeutic selection and resistance, particularly in the context of PARP inhibitor therapy. Identification of a pathogenic ''BRCA1/BRCA2'' variant in tumor tissue should prompt confirmatory germline testing to distinguish hereditary from purely somatic events. | '''Tumor testing:''' Tumor sequencing may identify somatic ''BRCA1/BRCA2'' alterations, loss of heterozygosity, or reversion mutations, which have implications for therapeutic selection and resistance, particularly in the context of PARP inhibitor therapy. Identification of a pathogenic ''BRCA1/BRCA2'' variant in tumor tissue should prompt confirmatory germline testing to distinguish hereditary from purely somatic events. | ||
==Additional Information== | ==Additional Information BRCA1 and BRCA2== | ||
* '''Founder mutations:''' Multiple recurrent pathogenic variants demonstrate strong population specific founder effects, most notably c.68_69delAG (185delAG) and c.5266dupC (5382insC) in ''BRCA1'', and c.5946delT (6174delT) in ''BRCA2'', particularly among individuals of Ashkenazi Jewish ancestry. Additional founder variants have been reported in Icelandic, Dutch, and other geographically or ethnically defined populations, underscoring the importance of ancestry-informed testing strategies. | |||
* '''Genotype–phenotype correlations:''' Although penetrance is variable, ''BRCA1'' pathogenic variants are disproportionately associated with triple-negative breast cancer, whereas ''BRCA2'' pathogenic variants are more commonly linked to hormone receptor–positive breast cancer and confer a higher risk of male breast and prostate cancers. These genotype-phenotype differences have implications for clinical presentation, surveillance, and therapeutic decision-making. | |||
* '''Therapeutic implications:''' Tumors with biallelic inactivation of ''BRCA1'' or ''BRCA2'' exhibit homologous recombination deficiency (HRD), resulting in increased sensitivity to platinum-based chemotherapy and PARP inhibitors. However, acquisition of secondary somatic reversion mutations that restore gene function represents a well-established mechanism of acquired therapeutic resistance, particularly following prolonged treatment exposure. | |||
* '''Risk management considerations:''' Identification of germline pathogenic variants in ''BRCA1'' or ''BRCA2'' has substantial implications for personalized cancer risk assessment, implementation of enhanced surveillance protocols, consideration of risk-reducing surgical interventions, and cascade testing of at risk relatives. | |||
* '''Overlap with other syndromes:''' ''BRCA1'' and ''BRCA2'' associated hereditary cancer predisposition shares molecular and clinical features with other DNA damage response and homologous recombination repair disorders, including syndromes caused by pathogenic variants in ''PALB2, ATM, CHEK2,'' and ''RAD51C/D''. These genes should be considered in differential diagnosis and comprehensive hereditary cancer panel testing. | |||
==Links== | ==Links== | ||
https://clinicalgenome.org/affiliation/50087/ | https://clinicalgenome.org/affiliation/50087/ | ||