Breast cancer treatment is multidisciplinary. Most women with early stage breast cancer are candidates for breast-conserving surgery with radiotherapy or mastectomy. The risk of local recurrence and the chance of survival does not differ with these approaches. Sentinel node biopsy is used for axillary staging, and individualized approaches are minimizing the need for axillary dissection in women with positive sentinel nodes. Adjuvant systemic therapy is used in most women based on proven survival benefit, and molecular profiling to individualize treatment based on risk is now a clinical reality for patients with hormone receptor-positive cancers.
BackgroundVariations in single nucleotide polymorphisms (SNPs) have been associated with enhanced drug efficacy and toxicity in cancer therapy. SNP variations in the ErbB2 gene have been identified that alter the protein sequence of the HER2-neu protein, but how these polymorphisms affect prognosis and response to HER2 targeted therapy is unknown. We examined eleven ErbB2 SNPs that alter the HER2-neu amino acid sequence to determine whether any of these particular polymorphisms were associated with increased trastuzumab cardiotoxicity in a case–control study.Methods140 subjects were enrolled from a single institution under Weill Cornell Medical College IRB protocol #0804009734. Patients were eligible if they had histologically or cytologically proven HER2-neu positive breast cancer and more than 3 months of trastuzumab therapy. Cases had either symptomatic CHF or a decline in LVEF of 15% (or if the LVEF <55%, a decline in LVEF of 10%) that resulted in at least temporary discontinuation of trastuzumab, whereas controls had no decline in their LVEF. Eleven ErbB2 single gene SNPs that resulted in an alteration in the HER2-neu protein amino acid sequence were studied. Single gene SNP analysis was carried out using SNP genotyping assays from genomic DNA obtained from peripheral blood or buccal swab.ResultsOnly two of the ErbB2 SNPs (Ile 655 Val and Pro 1170 Ala) were found to have variation. There was no association between codon 665 and cardiotoxicity; however the proline variant of amino acid 1170 was more likely than the alanine variant to be found in cases with trastuzumab cardiotoxicity (35% of case patients as compared to 17% of controls, p = 0.04). This association remained significant in multivariable analysis taking into account age, race, and history of hypertension (adjusted OR = 2.60, 95% CI = 1.02, 6.62, p = 0.046).ConclusionsThe Her2/neu Pro 1170 Ala polymorphism can be used to identify a subset of patients who are at increased risk of cardiotoxicity from trastuzumab therapy. Her2/neu single nucleotide polymorphisms may be useful in conjunction with other biomarkers to risk stratify patients in order to optimize clinical management.
Purpose
2015 NCCN guidelines recommend genetic counseling and germline BRCA mutation testing be offered to women under age 60 with triple negative breast cancer (TNBC). As a result of the 2010 ASCO/CAP guidelines in breast cancer, patients with breast cancers that are ER or PR low-positive (1–9% on immunohistochemistry) are no longer strictly considered to have TNBC and may not be referred for genetic counseling. However, the incidence of BRCA mutation in patients with hormone receptor (HR) low-positive breast cancers remains unknown, and current ASCO/CAP guidelines may result in under-testing for BRCA mutation.
Methods
We reviewed a prospectively maintained research database of breast cancer patients evaluated at UT MD Anderson Cancer Center between 2004 and 2014, identifying 314 patients with ER<10%, PR<10%, HER-2 neu negative breast cancers with known BRCA mutation status.
Results
314 patients had breast cancers expressing ER and PR <10%; 238 (75.8%) had HR negative (ER and PR <1%) cancers and 76 (24.2%) had HR low-positive (ER and/or PR 1–9%) cancers. Among patients with HR negative tumors, 86 of 238 (36.1%) had a BRCA 1/2 mutation, while among the HR low-positive group, 30 of 76 (39.5%) had a BRCA 1/2 mutation. In multivariate analysis, HR status (HR<1% vs. HR 1–9%) was not significantly associated with BRCA 1/2 mutation.
Conclusion
The incidence of BRCA 1/2 mutation is similar in patients with HR low-positive and HR negative breast cancers. We recommend offering genetic counseling and BRCA testing to patients under age 60 with ER low-positive breast cancers.
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