Considerations in Testing for Inherited Breast Cancer Predisposition in the Era of Personalized Medicine

The role of next-generation sequencing in the examination of signaling genes in Brca1/2-negative breast cancer cases

INTRODUCTION

Breast cancer is the most prevalent malignancy in women worldwide. Although pathogenic variants in the BRCA1/2 genes are responsible for the majority of hereditary breast cancer cases, a substantial proportion of patients are negative for pathogenic variations in these genes. In cancers, the signal transduction pathways of the cell are usually affected first. Therefore, this study aimed to detect and classified genetic variations in non-BRCA signaling genes and investigate the underlying genetic causes of susceptibility to breast cancer.

METHODS

Ninety-six patients without pathogenic variants in the BRCA1/2 genes who met the inclusion criteria were enrolled in the study, and 34 genes were analyzed using next-generation sequencing (NGS) for genetic analysis.

RESULTS

Based on the ClinVar database or American College of Medical Genetics criteria, a total of 55 variants of 16 genes were detected in 43 (44.8%) of the 96 patients included in the study. The pathogenic variants were found in the TP53, CHEK2, and RET genes, whereas the likely pathogenic variants were found in the FGFR1, FGFR3, EGFR, and NOTCH1 genes.

CONCLUSION

The examination of signaling genes in patients who met the established criteria for hereditary breast cancer but were negative for BRCA1/2 pathogenic variants provided additional information for approximately 8% of the families. The results of the present study suggest that NGS is a powerful tool for investigating the underlying genetic causes of occurrence and progression of breast cancer.

Guideline-Based, Multi-Gene Panel Germline Genetic Testing for at-Risk Patients with Breast Cancer

Background

Genetic testing for at-risk patients with breast cancer should be routinely offered. Knowledge generated may influence both treatment decisions and cancer prevention strategies among the patients themselves and their relatives. In this study, we report on the prevalence and patterns of germline mutations, using commercially available next-generation sequencing (NGS)-based multi-gene panels (MGP).

Patients and Methods

Consecutive at-risk breast cancer patients, as determined by international guidelines, were offered germline genetic testing using a 20-gene NGS-based panel at a reference lab. Samples of peripheral blood were obtained for DNA extraction and genetic variants were classified as benign/likely benign (negative), pathogenic/likely pathogenic (positive) or variants of uncertain significance (VUS).

Results

A total of 1310 patients, median age (range) 43 (19-82) years, were enrolled. Age ≤45 years (n = 800, 61.1%) was the most common indication for testing. Positive family history of breast, ovarian, pancreatic or prostate cancers, and triple-negative disease were among the common indications. Among the whole group, 184 (14.0%) patients had pathogenic/likely pathogenic variants; only 90 (48.9%) were in BRCA1 or BRCA2, while 94 (51.9%) others had pathogenic variants in other genes; mostly in APC, TP53, CHEK2 and PALB2. Mutation rates were significantly higher among patients with positive family history (p = 0.009); especially if they were 50 years or younger at the time of breast cancer diagnosis (p < 0.001). Patients with triple-negative disease had relatively higher rate (17.5%), and mostly in BRCA1/2 genes (71.4%). Variants of uncertain significance (VUS) were reported in 559 (42.7%) patients; majority (90.7%) were in genes other than BRCA1 or BRCA2.

Conclusion

Pathogenic mutations in genes other than BRCA1/2 are relatively common and could have been missed if genetic testing was restricted to BRCA1/2. The significantly high rate of VUS associated with multi-gene panel testing can be disturbing.

Risk‐reducing mastectomy decisions among women with mutations in high‐ and moderate‐ penetrance breast cancer susceptibility genes

Background

Women harboring mutations in breast cancer susceptibility genes are at increased lifetime risk of developing breast cancer and are faced with decisions about risk management, including whether to undergo high‐risk screening or risk‐reducing mastectomy (RRM). National guidelines recommend BRCA1 or BRCA2 mutation carriers consider RRM, but that carriers of moderate penetrance mutations (e.g., ATM or CHEK2) should be managed based on family history. We aimed to investigate determinants of decision for RRM, and hypothesized that mutation status, age, family history, partner status, and breast cancer would impact RRM decision making.

Methods

We performed a retrospective study assessing RRM decisions for 279 women.

Results

Women with BRCA and moderate penetrance gene mutations, a personal history of breast cancer, or a first degree relative with a history of breast cancer were more likely to undergo RRM. Breast cancer status and age showed an interaction effect such that women with breast cancer were less likely to undergo RRM with increasing age.

Conclusion

Although national guidelines do not recommend RRM for moderate penetrance carriers, the rates of RRM for this population approached those for BRCA mutation carriers. Further insights are needed to better support RRM decision‐making in this population.

Referencing BRCA in hereditary cancer risk discussions: In search of an anchor in a sea of uncertainty

As panel testing and exome sequencing are increasingly incorporated into clinical care, clinicians must grapple with how to communicate the risks and treatment decisions surrounding breast cancer genes beyond BRCA1 and BRCA2. In this paper, we examine clinicians' practice of employing BRCA1 and BRCA2 to help contextualize less certain genetic information regarding cancer risk and the possible implications of this practice for patients within the context of an exome sequencing study, NCGENES. We audio-recorded return of results appointments for 14 women who participated in NCGENES, previously had breast cancer, and were suspected of having a hereditary cancer predisposition. These patients were also interviewed four weeks later regarding their understanding of their results. We found that BRCA1 and BRCA2 were held as the gold standard, where clinicians compared what is known about BRCA to the limited understanding of other breast cancer-related genes. BRCA1 and BRCA2 were used as anchors to shape patients' understandings of genetic knowledge, risk, and management, illustrating how the information clinicians provide to patients may work as an external anchor. Yet, presenting BRCA1 and BRCA2 as a means of scientific reassurance can run the risk of patients conflating knowledge about certainty of risk with degree of risk after receiving a result for a moderate penetrance gene. This can be further complicated by misperceptions of the precision of cancer predictability attributed to these or other described 'cancer genes' in public media.

Multi gene panel testing for hereditary breast cancer - is it ready to be used?

Breast cancer is one of the most common malignancies and the leading cause of death among women worldwide. About 20% of breast cancers are hereditary. Approximately 30% of the mutations have remained negative after testing BRCA1/2 even in families with a Mendelian inheritance pattern for breast cancer. Additional non-BRCA genes have been identified as predisposing for breast cancer. Multi gene panel testing tries to cover and explain the BRCA negative inherited breast cancer, improving efficiency, speed and costs of the breast cancer screening. We identified 23 studies reporting results from individuals who have undergone multi gene panel testing for hereditary breast cancer and noticed a prevalence of 1-12% of non-BRCA genes, but also a high level of variants of uncertain significance. A result with a high level of variants of uncertain significance is likely to be more costly than bring benefits, as well as increase the anxiety for patients. Regarding further development of multi gene panel testing, more research is required to establish both the optimal care of patients with cancer (specific treatments like PARP inhibitors) and the management of unaffected individuals (chemoprevention and/or prophylactic surgeries). Early detection in these patients as well as prophylactic measures will significantly increase the chance of survival. Therefore, multi gene panel testing is not yet ready to be used outside clear guidelines. In conclusion, studies on additional cohorts will be needed to better define the real prevalence, penetrance and the variants of these genes, as well as to describe clear evidence-based guidelines for these patients.

Trends in use of bilateral prophylactic mastectomy vs high-risk surveillance in unaffected carriers of inherited breast cancer syndromes in the Inherited Cancer Registry (ICARE)

PURPOSE

Awareness of inherited breast cancer has increased bilateral prophylactic mastectomy (BPM) among unaffected genetic mutation carriers, yet many still choose surveillance. We aimed to identify differences among women electing BPM vs high-risk surveillance.

METHODS

Participants from an IRB-approved database recruited from 11/2000 to 01/2017 with a deleterious/pathogenic, variant suspected deleterious, or likely pathogenic mutation in ≥ 1 of 11 genes with increased risk for breast cancer (per 2017 NCCN guidelines) were identified. Participants with breast cancer and males were excluded. Sociodemographic and clinical data were collected. The BPM and high-risk surveillance groups were compared using Wilcoxon, Fisher's Exact, and Pearson's Chi-Square analyses.

RESULTS

A total of 304 unaffected genetic mutation carriers were identified; 22 men were excluded. 113/282 (40%) underwent BPM. There was no significant difference in age, race, marital status, high school graduates, family history of breast cancer, breast biopsies, chemoprevention use, or understanding implications of genetic mutation carriage. BPM participants were more likely to have a prior pregnancy (p = 0.0005), college education (p = 0.04), income > $50,000/year (p = 0.01), first-degree relative with breast cancer (p = 0.04), higher total number of relatives with breast cancer (p = 0.01), and rate of risk-reducing salpingo-oophorectomy (p = < 0.0001). The high-risk surveillance group was more likely to have a history of ovarian cancer (p = 0.009) and cancer worry (p = < 0.0001).

CONCLUSIONS

BPM is a common but not universal choice among unaffected genetic carriers of inherited breast cancer syndromes. Parity, education, income, ovarian cancer history, first-degree relatives with breast cancer, and cancer worry play significant roles in these decisions.