Fanconi anaemia, BRCA2 and familial considerations - follow up on a previous case report

The BRCA2 variant c.68-7 T>A is associated with breast cancer

Background

BRCA2 c.68-7T>A has been demonstrated to cause aberrant splicing and is possibly pathogenic. The population prevalence of the variant is 0.2%, which higher than usual for pathogenic BRCA2 variants. The pathogenicity of the variant is discussed.

Methods

The outpatient genetic clinic at The Norwegian Radium Hospital, part of Oslo University Hospital, has invited breast cancer kindreds for genetic examinations and prospective follow-up of high risk patients since 1988. We have complete files of all activities and results, and we examined the files for association between BRCA2 c.68-7T>A and breast cancer.

Results

Seventeen out of 714 (2.4%) breast cancer kindreds sequenced for BRCA2 carried the variant BRCA2 c.68-7T>A (p < 0.0001 compared to population controls). Segregation analysis was inconclusive (likelihood ratio 0.36) for pathogenicity. Two breast cancers were prospectively observed during 134 observation years (annual incidence rate 1.5% (95% CI 0.15% to 5.4%) and one additional breast cancer was diagnosed at first (prevalence) round.

Conclusion

BRCA2 c.68-7T>A is associated with breast cancer. In the families selected due to aggregation of breast cancer, carriers of the BRCA2 c.68-7T>A variant have increased risk for breast cancer. It is, however, possible that the variant has lower penetrance than the average pathogenic BRCA2 variants, and that in the families selected for having known aggregation of breast cancer other (modifying) factors contributed to the observed results.

Preemptive Bone Marrow Transplantation for FANCD1/BRCA2

Children with biallelic mutations in FANCD1/BRCA2 are at uniquely high risks of leukemia and solid tumors. Preemptive bone marrow transplantation (PE-BMT) has been proposed to avoid the development of leukemia, but empirical study of PE-BMT is unlikely because of the rarity of these children and the unknown benefit of PE-BMT. We used survival analysis to estimate the risks of leukemia and the expected survival if leukemia could be eliminated by curative PE-BMT. We used the results in a decision analysis model to explore the plausibility of PE-BMT for children with variable ages at diagnosis and risks of transplantation-related mortality. For example, PE-BMT at 1 year of age with a 10% risk of transplantation-related mortality increased the mean survival by 1.7 years. The greatest benefit was for patients diagnosed between 1 and 3 years of age, after which the benefit of PE-BMT decreased with age at diagnosis, and the risk of death from solid tumors constituted a relatively greater burden of mortality. Our methods may be used to model survival for other hematologic disorders with limited empirical data and a pressing need for clinical guidance.

Characterization of medulloblastoma in Fanconi Anemia: a novel mutation in the BRCA2 gene and SHH molecular subgroup

Fanconi Anemia (FA) is an inherited disorder characterized by the variable presence of multiple congenital somatic abnormalities, bone marrow failure and cancer susceptibility. Medulloblastoma (MB) has been described only in few cases of FA with biallelic inactivation in the tumor suppressor gene BRCA2/FANCD1 or its associated gene PALB2/FANCN.

We report the case of a patient affected by Fanconi Anemia with Wilms tumor and unusual presentation of two medulloblastomas (MB1 and MB2). We identified a new pathogenetic germline BRCA2 mutation: c.2944_2944delA. Molecular analysis of MBs allowed us to define new features of MB in FA. MBs were found to belong to the Sonic Hedgehog (SHH) molecular subgroup with some differences between MB1 and MB2. We highlighted that MB in FA could share molecular aspects and hemispheric localization with sporadic adult SHH-MB. Our report provides new findings that shed new light on the genetic and molecular pathogenesis of MB in FA patients with implications in the disease management.

Fanconi anaemia, BRCA2 mutations and childhood cancer: a developmental perspective from clinical and epidemiological observations with implications for genetic counselling

Fanconi anaemia (FA) is an inherited condition characterised by congenital and developmental abnormalities and a strong cancer predisposition. In around 3-5% of cases FA is caused by biallelic mutations in the BRCA2 gene. Individuals heterozygous for BRCA2 mutations have an increased risk of inherited breast and ovarian cancer. We reviewed the mutation spectrum in BRCA2-associated FA, and the spectrum and frequency of BRCA2 mutations in distinct populations. The rarity of FA due to biallelic BRCA2 mutations supports a fundamental role of BRCA2 for prevention of malignant transformation during development. The spectrum of malignancies seen associated with FA support the concept of a tissue selectivity of BRCA2 mutations for development of FA-associated cancers. This specificity is illustrated by the distinct FA-associated BRCA2 mutations that appear to predispose to specific brain or haematological malignancies. For some populations, the number of FA-patients with biallelic BRCA2 disruption is smaller than that expected from the carrier frequency, and this implies that some pregnancies with biallelic BRCA2 mutations do not go to term. The apparent discrepancy between expected and observed incidence of BRCA2 mutation-associated FA in high-frequency carrier populations has important implications for the genetic counselling of couples with recurrent miscarriages from high-risk populations.