BRCA1/2 reversion mutations in a pan-cancer cohort

Tumor sensitivity to platinum (Pt)-based chemotherapy and poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors is increased by homologous recombination deficiency-causing mutations; in particular, reversion mutations cause drug resistance by restoring protein function. Treatment response is predicted by breast cancer susceptibility gene 1/2 (BRCA1/2) mutations; however, BRCA1/2 reversion mutations have not been comprehensively studied in pan-cancer cohorts. We aimed to characterize BRCA1/2 reversion mutations in a large pan-cancer cohort of Japanese patients by retrospectively analyzing sequencing data for BRCA1/2 pathogenic/likely pathogenic mutations in 3738 patients with 32 cancer types. We identified somatic mutations in tumors or circulating cell-free DNA that could restore the ORF of adverse alleles, including reversion mutations. We identified 12 (0.32%) patients with somatic BRCA1 (n = 3) and BRCA2 (n = 9) reversion mutations in breast (n = 4), ovarian/fallopian tube/peritoneal (n = 4), pancreatic (n = 2), prostate (n = 1), and gallbladder (n = 1) cancers. We identified 21 reversion events-BRCA1 (n = 3), BRCA2 (n = 18)-including eight pure deletions, one single-nucleotide variant, six multinucleotide variants, and six deletion-insertions. Seven (33.3%) reversion deletions showed a microhomology length greater than 1 bp, suggesting microhomology-mediated end-join repair. Disease course data were obtained for all patients with reversion events: four patients acquired mutations after PARP-inhibitor treatment failure, two showed somatic reversion mutations after disease progression, following Pt-based treatment, five showed mutations after both treatments, one patient with pancreatic cancer and BRCA1 reversion mutations had no history of either treatment. Although reversion mutations commonly occur in BRCA-associated cancers, our findings suggest that reversion mutations due to Pt-chemotherapy might be correlated with BRCA1/2-mediated tumorigenesis even in non-BRCA-associated histologies.

Breast cancer in East Africa: Prevalence and spectrum of germline SNV/indel and CNVs in BRCA1 and BRCA2 genes among breast cancer patients in Tanzania

BACKGROUND

Growing prevalence and aggressiveness of breast cancer (BC) among East African women strongly indicate that the genetic risk factor implicated in the etiology of the disease may have a key role. Germline pathogenic variants in BRCA1 and BRCA2 (BRCA1/2) are known to increase the lifetime risk of BC. This study investigated the prevalence and spectrum of germline single nucleotide variant/insertion and deletion (SNV/indel), and copy number variations (CNVs) in BRCA1/2 among Tanzanian BC patients, and evaluated the associations of identified variants with patient's socio-demographic and histopathological characteristics.

METHODS

One hundred BC patients were examined for BRCA1/2 variants using next-generation sequencing (NGS). Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) assay were performed for the confirmation of SNV/indel and CNVs, respectively.

RESULTS

Six germline SNV/indel pathogenic variants were detected from six unrelated patients. Five of these variants were identified in BRCA1, and one in BRCA2. We also identified, in one patient, one variant of uncertain clinical significance (VUS). CNV was not detected in any of the BC patients. Furthermore, we found that in our cohort, BRCA1/2 variant carriers were triple-negative BC patients (p = 0.019).

CONCLUSIONS

Our study provides first insight into BC genetic landscape by the use of NGS in the under-represented East African Tanzanian populations. Our findings support the importance of genetic risk factors in BC etiology in Tanzania and showed a relatively high overall prevalence (6%) of germline BRCA1/2 pathogenic variants in BC patients. Therefore, our results indicate that BRCA1/2 pathogenic variants may well contribute to BC incidence in Tanzania. Thus, the identification of frequent variants in BRCA1/2 genes will enable implementation of rapid, inexpensive population-specific BRCA1/2 genetic testing, particularly for triple-negative BC patients known for their high prevalence in Tanzania. This will, in turn, greatly contributes to provide effective therapeutic strategies.

BRCA1/2 testing among young women with breast cancer in Massachusetts, 2010-2013: An observational study using state cancer registry and All-Payer claims data

Background

Testing for BRCA1/2 pathogenic variants is recommended for women aged ≤45 years with breast cancer. Some studies have found racial/ethnic and socioeconomic disparities in testing. We linked Massachusetts' All‐Payer Claims Database with Massachusetts Cancer Registry data to assess factors associated with BRCA1/2 testing among young women with breast cancer in Massachusetts, a state with high levels of access to care and equitable insurance coverage of breast cancer gene (BRCA) testing.

Methods

We identified breast cancer diagnoses in the Massachusetts Cancer Registry from 2010 to 2013 and linked registry data with Massachusetts All‐Payer Claims Data from 2010 to 2014 among women aged ≤45 years with private insurance or Medicaid. We used multivariable logistic regression to examine factors associated with BRCA1/2 testing within 6 months of diagnosis.

Results

The study population included 2424 women; 80.3% were identified as non‐Hispanic White, 6.4% non‐Hispanic Black, and 6.3% Hispanic. Overall, 54.9% received BRCA1/2 testing within 6 months of breast cancer diagnosis. In adjusted analyses, non‐Hispanic Black women had less than half the odds of testing compared with non‐Hispanic White women (adjusted odds ratio [OR] = 0.45, 95% CI = 0.31, 0.64). Medicaid‐insured women had half the odds of testing compared with privately‐insured women (OR = 0.51, 95% CI = 0.41, 0.63). Living in lower‐income areas was also associated with lower odds of testing. Having an academically‐affiliated oncology clinician was not associated with testing.

Conclusion

Socioeconomic and racial/ethnic disparities exist in BRCA1/2 testing among women with breast cancer in Massachusetts, despite equitable insurance coverage of testing. Further research should examine whether disparities have persisted with growing testing awareness and availability over time.