Gene-panel testing of breast and ovarian cancer patients identifies a recurrent RAD51C duplication

Gene-panel sequencing allows comprehensive analysis of multiple genes simultaneously and is now routinely used in clinical mutation testing of high-risk breast and ovarian cancer patients. However, only BRCA1 and BRCA2 are often analyzed also for large genomic changes. Here, we have analyzed 10 clinically relevant susceptibility genes in 95 breast or ovarian cancer patients with gene-panel sequencing including also copy number variants (CNV) analysis for genomic changes. We identified 12 different pathogenic BRCA1, BRCA2, TP53, PTEN, CHEK2, or RAD51C mutations in 18 of 95 patients (19%). BRCA1/2 mutations were observed in 8 patients (8.4%) and CHEK2 protein-truncating mutations in 7 patients (7.4%). In addition, we identified a novel duplication encompassing most of the RAD51C gene. We further genotyped the duplication in breast or ovarian cancer families (n = 1149), in unselected breast (n = 1729) and ovarian cancer cohorts (n = 553), and in population controls (n = 1273). Seven additional duplication carries were observed among cases but none among controls. The duplication associated with ovarian cancer risk (3/590 of all ovarian cancer patients, 0.5%, P = .032 compared with controls) and was found to represent a large fraction of all identified RAD51C mutations in the Finnish population. Our data emphasizes the importance of comprehensive mutation analysis including CNV detection in all the relevant genes.

Abstract P3-09-01: BRCAsearch - results of population-based screening of BRCA1 and BRCA2 germline mutations in incident breast cancer in South Sweden

Increasing evidence supports the benefit of identifying the BRCA1 and BRCA2 germline mutation status in early breast cancer. Germline mutations in these two genes are treatment predictive for the benefit of risk reducing surgical interventions of the contralateral breast and the ovaries and fallopian tubes, in early breast cancer (Metcalf 2014; Domchek 2010). Furthermore, they may possibly also be treatment predictive for the effect of certain types of medical interventions (Tutt SABCS 2014).

In order to provide the patient with the opportunity to take BRCA test results into account already when planning primary treatment, BRCA testing and cancer genetic counseling needs to be initiated and performed early during the diagnostic and treatment related process in newly diagnosed breast cancer cases. Special attention needs to be taken to the fact that the test results may affect not only the patient, but also her or his relatives. We have observed that the clinical efficacy of BRCA-screening criteria may be surprisingly low, leaving a substantial number of BRCA-carriers undetected in spite of intense contacts with health care providers (Unpublished results).

BRCAsearch (ClinicalTrials.gov Identifier: NCT02557776) is a population based study including new invasive breast cancer cases at three hospitals in the South of Sweden. Patients are invited to perform BRCA1 and BRCA2 germline mutation analysis at time of primary treatment after written study information and written genetic counseling, irrespective of family history, age or clinical phenotype. The primary end-points of the study include the rate of BRCA mutations in newly diagnosed breast cancer in South Sweden, the fraction of patients that accept inclusion in the study, and the rate of mutation positive patients that do not fulfill clinical criteria for BRCA mutation screening. Secondary end-points include the perception among patient of the intervention and testing procedures, the types of questions the patients present during the process and psychosocial outcome among carriers and non-carriers.

In May 2016 about 400 patients have been included in the study, whereof 333 have been analyzed for BRCA germline mutations. The accrual target of the study is 500 patients, which will be reached during the fall of 2016. At the meeting, the BRCA1 and BRCA2 mutation rates will be presented, as well as the acceptance rate of the study among patients approached, and the fraction of mutation positive patients that do not fulfill current BRCA1 and BRCA2 mutation screening criteria, and whose positive mutation status therefore would have been missed if clinical selection criteria had been applied.

The results of the study will be used to define selection criteria for BRCA-mutation screening in new breast cancer cases, and the design of screening procedures with an appropriate clinical effectiveness.Increasing evidence supports the benefit of identifying the BRCA1 and BRCA2 germline mutation status in early breast cancer. Germline mutations in these two genes are treatment predictive for the benefit of risk reducing surgical interventions of the contralateral breast and the ovaries and fallopian tubes, in early breast cancer (Metcalf 2014; Domchek 2010). Furthermore, they may possibly also be treatment predictive for the effect of certain types of medical interventions (Tutt SABCS 2014).

In order to provide the patient with the opportunity to take BRCA test results into account already when planning primary treatment, BRCA testing and cancer genetic counseling needs to be initiated and performed early during the diagnostic and treatment related process in newly diagnosed breast cancer cases. Special attention needs to be taken to the fact that the test results may affect not only the patient, but also her or his relatives. We have observed that the clinical efficacy of BRCA-screening criteria may be surprisingly low, leaving a substantial number of BRCA-carriers undetected in spite of intense contacts with health care providers (Unpublished results).

BRCAsearch (ClinicalTrials.gov Identifier: NCT02557776) is a population based study including new invasive breast cancer cases at three hospitals in the South of Sweden. Patients are invited to perform BRCA1 and BRCA2 germline mutation analysis at time of primary treatment after written study information and written genetic counseling, irrespective of family history, age or clinical phenotype. The primary end-points of the study include the rate of BRCA mutations in newly diagnosed breast cancer in South Sweden, the fraction of patients that accept inclusion in the study, and the rate of mutation positive patients that do not fulfill clinical criteria for BRCA mutation screening. Secondary end-points include the perception among patient of the intervention and testing procedures, the types of questions the patients present during the process and psychosocial outcome among carriers and non-carriers.

In May 2016 about 400 patients have been included in the study, whereof 333 have been analyzed for BRCA germline mutations. The accrual target of the study is 500 patients, which will be reached during the fall of 2016. At the meeting, the BRCA1 and BRCA2 mutation rates will be presented, as well as the acceptance rate of the study among patients approached, and the fraction of mutation positive patients that do not fulfill current BRCA1 and BRCA2 mutation screening criteria, and whose positive mutation status therefore would have been missed if clinical selection criteria had been applied.

The results of the study will be used to define selection criteria for BRCA-mutation screening in new breast cancer cases, and the design of screening procedures with an appropriate clinical effectiveness.

Citation Format: Loman N, Borg Å, Henriksson K, Kristoffersson U, Kvist A, Silfverberg B, Törngren T, Brandberg Y, Nilsson M. BRCAsearch - results of population-based screening of BRCA1 and BRCA2 germline mutations in incident breast cancer in South Sweden [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-09-01.

Targeted sequencing of BRCA1 and BRCA2 across a large unselected breast cancer cohort suggests that one-third of mutations are somatic

We carried out targeted sequencing of BRCA1/2 in an unselected cohort of patients diagnosed with primary breast cancer within a population without strong founder mutations. Eleven percent of cases harbored a germline or somatic BRCA1/2 mutation, and the ratio of germline versus somatic mutation was 2 : 1. This has implications for treatment, genetic counseling, and interpretation of tumor-only testing.

Background

A mutation found in the BRCA1 or BRCA2 gene of a breast tumor could be either germline or somatically acquired. The prevalence of somatic BRCA1/2 mutations and the ratio between somatic and germline BRCA1/2 mutations in unselected breast cancer patients are currently unclear.

Patients and methods

Paired normal and tumor DNA was analyzed for BRCA1/2 mutations by massively parallel sequencing in an unselected cohort of 273 breast cancer patients from south Sweden.

Results

Deleterious germline mutations in BRCA1 (n = 10) or BRCA2 (n = 10) were detected in 20 patients (7%). Deleterious somatic mutations in BRCA1 (n = 4) or BRCA2 (n = 5) were detected in 9 patients (3%). Accordingly, about 1 in 9 breast carcinomas (11%) in our cohort harbor a BRCA1/2 mutation. For each gene, the tumor phenotypes were very similar regardless of the mutation being germline or somatically acquired, whereas the tumor phenotypes differed significantly between wild-type and mutated cases. For age at diagnosis, the patients with somatic BRCA1/2 mutations resembled the wild-type patients (median age at diagnosis, germline BRCA1: 41.5 years; germline BRCA2: 49.5 years; somatic BRCA1/2: 65 years; wild-type BRCA1/2: 62.5 years).

Conclusions

In a population without strong germline founder mutations, the likelihood of a BRCA1/2 mutation found in a breast carcinoma being somatic was ∼1/3 and germline 2/3. This may have implications for treatment and genetic counseling.

Abstract OT2-05-01: BRCAsearch: A population based prospective study on screening for BRCA1 and BRCA2 germline mutations in patients with newly diagnosed breast cancer treated in southern Sweden

The overall purpose of the study BRCAsearch is to evaluate a new method for offering mutation analysis of BRCA1 and BRCA2 to all patients with newly diagnosed breast cancer.

Patients with breast cancer in southern Sweden are offered inclusion in the SCAN-B study at the time of diagnosis pre-surgery. If they consent, a part of the tumor is sent to a lab in Lund, Sweden, for research purposes (RNA sequencing etc.). Patients that are included in the SCAN-B study are eligible for inclusion in BRCAsearch.

Summary of study procedure for BRCAsearch:

1.An envelope with written information is given to the patient at the visit to the surgeon the week after surgery. This envelope contains a written genetic counseling, information about the study, an informed consent form, psychosocial questionnaires and contact information to a genetic counsellor and psycisians responsible for the study (telephone, e-mail). The patient can contact a genetic counselor for pre-test telephone genetic counseling if she wishes to.

2.BRCA1 and BRCA2 are analyzed.

3.Non-carriers are informed about the test result with a letter. Mutation carriers and VUS (variants of uncertain significance) are telephoned and given a time for an appointment at the Department of Clinical Genetics.

4.Psychosocial self-reported questionnaires are delivered at 3 times over a year.

Inclusion criteria (all):

1.The patient is included in the SCAN-B study.

2.The patient is recently diagnosed with an invasive breast cancer or a ductal cancer in situ.

3.The patient has signed an informed consent form for BRCAsearch.

Exclusion criteria (any of):

1.The patient is unable to understand the written information in Swedish.

2.The patient is a psychological state, due to chronic och temporary reasons, where one could suspect that information about the study substantially could be detrimental to the psychological well-beeing.

Primary outcome measures:

• Prevalence of BRCA1/2 mutations in an unselected breast cancer cohort in southern Sweden

• Uptake of genetic testing

• Proportion of the mutation carriers that do not fulfil current criteria for genetic testing

Secondary outcome measures:

• How many of the patients that contact us for questions and what type of questions they have

• How uptake of genetic testing varies with patient, treatment, and tumor characteristics

• The patients' attitudes towards the method used for identifying mutation carriers

• The economic cost per QALY (quality-adjusted life year)

• Psychosocial comparisons between mutation carriers and non-carriers

Targeted accrual is 500 patients included in the study, which is expected to be reached by the end of 2016.

The study enrolls patients from two hospitals in southern Sweden:

1.Helsingborg Hospital (study start: Febuary 2, 2015)

2.Kristianstad Hospital (study start: March 2, 2015).

Citation Format: Nilsson MP, Borg Å, Henriksson K, Kristoffersson U, Kvist A, Silfverberg B, Törngren T, Loman N. BRCAsearch: A population based prospective study on screening for BRCA1 and BRCA2 germline mutations in patients with newly diagnosed breast cancer treated in southern Sweden. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT2-05-01.