Do women remain at risk even if they do not inherit a familial BRCA1/2 mutation?

Survey of primary care physicians' views about breast and ovarian cancer screening for true BRCA1/2 non-carriers

Despite some controversy, true BRCA1/2 non-carriers are generally considered to be at an average risk for breast and ovarian cancer. Primary care physicians are then expected to encourage their non-carrier patients to adopt cancer screening practices appropriate to women of the same age in the general population. This study aimed to describe breast and ovarian cancer screening recommendations that primary care physicians would consider advisable for young true BRCA1/2 non-carriers. One hundred thirty-four family physicians and 123 gynecologists (response rate 45%) completed a cross-sectional mailed survey administered in the Province of Quebec, Canada. The survey included questions about basic genetic knowledge and screening recommendations for two fictitious cases (< 40 years), one carrier and one non-carrier, from a BRCA1/2 mutation-positive family. Screening exams considered advisable did not differ significantly between family physicians and gynecologists. More than 75% of physicians considered the cancer risks of true non-carriers to be comparable with that of the general population and 14% to be a little higher. Still, 53% would prescribe a biennial and or even an annual (27%) mammography to a non-carrier woman before the recommended starting age. Physician considerations of non-carriers' expectations or requests for screening were associated with more screening prescriptions. More than half of primary care physicians would recommend more mammography screenings than expected for a young true BRCA1/2 non-carrier. Personalized cancer risk assessment may help primary care physicians tailor screening of women from BRCA1/2 mutation-positive families and allow these women to make more informed choices regarding cancer risk management options.

Somatic variants of potential clinical significance in the tumors of BRCA phenocopies

BACKGROUND

BRCA phenocopies are individuals with the same phenotype (i.e. cancer consistent with Hereditary Breast and Ovarian Cancer syndrome = HBOC) as their affected relatives, but not the same genotype as assessed by blood germline testing (i.e. they do not carry a germline BRCA1 or BRCA2 mutation). There is some evidence of increased risk for HBOC-related cancers in relatives of germline variant carriers even though they themselves test negative for the familial variant (BRCA non-carriers). At this time, BRCA phenocopies are recommended to undergo the same cancer surveillance as individuals in the general population. This raises the question of whether the increased cancer risk in BRCA non-carriers is due to alterations (germline, somatic or epigenetic) in other cancer-associated genes which were not analyzed during BRCA analysis.

METHODS

To assess the nature and potential clinical significance of somatic variants in BRCA phenocopy tumors, DNA from BRCA non-carrier tumor tissue was analyzed using next generation sequencing of 572 cancer genes. Tumor diagnoses of the 11 subjects included breast, ovarian, endometrial and primary peritoneal carcinoma. Variants were called using FreeBayes genetic variant detector. Variants were annotated for effect on protein sequence, predicted function, and frequency in different populations from the 1000 genomes project, and presence in variant databases COSMIC and ClinVar using Annovar.

RESULTS

None of the familial BRCA1/2 mutations were found in the tumor samples tested. The most frequently occurring somatic gene variants were ROS1(6/11 cases) and NUP98 (5/11 cases). BRCA2 somatic variants were found in 2/6 BRCA1 phenocopies, but 0/5 BRCA2 phenocopies. Variants of uncertain significance were found in other DNA repair genes (ERCC1, ERCC3, ERCC4, FANCD2, PALB2), one mismatch repair gene (PMS2), a DNA demethylation enzyme (TET2), and two histone modifiers (EZH2, SUZ12).

CONCLUSIONS

Although limited by a small sample size, these results support a role of selected somatic variants and epigenetic mechanisms in the development of tumors in BRCA phenocopies.

Can chimerism explain breast/ovarian cancers in BRCA non-carriers from BRCA-positive families?

Hereditary breast and ovarian cancer syndrome (HBOC) is most frequently caused by mutations in BRCA1 or BRCA2 (in short, BRCA) genes. The incidence of hereditary breast and ovarian cancer in relatives of BRCA mutation carriers who test negative for the familial mutation (non-carriers) may be increased. However, the data is controversial, and at this time, these individuals are recommended the same cancer surveillance as general population. One possible explanation for BRCA phenocopies (close relatives of BRCA carriers who have developed cancer consistent with HBOC but tested negative for a familial mutation) is natural chimerism where lack of detectable mutation in blood may not rule out the presence of the mutation in the other tissues. To test this hypothesis, archival tumor tissue from eleven BRCA phenocopies was investigated. DNA from the tumor tissue was analyzed using sequence-specific PCR, capillary electrophoresis, and pyrosequencing. The familial mutations were originally detected in the patients’ first-degree relatives by commercial testing. The same testing detected no mutations in the blood of the patients under study. The test methods targeted only the known familial mutation in the tumor tissue. Tumor diagnoses included breast, ovarian, endometrial and primary peritoneal carcinoma. None of the familial mutations were found in the tumor samples tested. These results do not support, but do not completely exclude, the possibility of chimerism in these patients. Further studies with comprehensive sequence analysis in a larger patient group are warranted as a chimeric state would further refine the predictive value of genetic testing to include BRCA phenocopies.

No evidence of excessive cancer screening in female noncarriers from BRCA1/2 mutation-positive families

BACKGROUND

In families with a proven BRCA1/2 mutation, women not carrying the familial mutation should follow the cancer screening recommendations applying to women in the general population. In the present study, we evaluated the cancer screening practices of unaffected noncarriers from families with a proven BRCA mutation, and we assessed the role of family history in their screening practices.

METHODS

Self-report data were provided retrospectively by 220 unaffected female noncarriers for periods of up to 10 years (mean: 4.3 years) since disclosure of their BRCA1/2 genetic test result. A ratio for the annual frequency of breast and ovarian cancer screening exams (mammography, breast ultrasonography, breast magnetic resonance imaging, transvaginal or pelvic ultrasound, cancer antigen 125 testing) was calculated as number of screening exams divided by the number of years in the individual observation period.

RESULTS

The annual average for mammography exams was 0.15, 0.4, 0.56, and 0.71 in women 30-39, 40-49, 50-59, and 60-69 years of age respectively. The uptake of other breast and ovarian cancer screening exams was very low. Mammography and breast ultrasonography and magnetic resonance imaging were generally more frequent among participants with at least 1 first-degree relative affected by breast cancer.

CONCLUSIONS

In most noncarriers, screening practices are consistent with the guidelines concerning women in the general population. When noncarriers adopt screening behaviours that are different from those that would be expected for average-risk women, those behaviours are influenced by their familial cancer history.

IMPACT

Decision tools might help female noncarriers to be involved in their follow-up in accordance with their genetic status and their family history, while taking into account the benefits and disadvantages of cancer screening.