Muriel A. Adank

Risks of breast, ovarian, and contralateral breast cancer for BRCA1 and BRCA2 mutation carriers

Importance The clinical management of BRCA1 and BRCA2 mutation carriers requires accurate, prospective cancer risk estimates. Objectives To estimate age-specific risks of breast, ovarian, and contralateral breast cancer for mutation carriers and to evaluate risk modification by family cancer history and mutation location. Design, Setting, and Participants Prospective cohort study of 6036 BRCA1 and 3820 BRCA2 female carriers (5046 unaffected and 4810 with breast or ovarian cancer or both at baseline) recruited in 1997-2011 through the International BRCA1/2 Carrier Cohort Study, the Breast Cancer Family Registry and the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer, with ascertainment through family clinics (94%) and population-based studies (6%). The majority were from large national studies in the United Kingdom (EMBRACE), the Netherlands (HEBON), and France (GENEPSO). Follow-up ended December 2013; median follow-up was 5 years. Exposures BRCA1/2 mutations, family cancer history, and mutation location. Main Outcomes and Measures Annual incidences, standardized incidence ratios, and cumulative risks of breast, ovarian, and contralateral breast cancer. Results Among 3886 women (median age, 38 years; interquartile range [IQR], 30-46 years) eligible for the breast cancer analysis, 5066 women (median age, 38 years; IQR, 31-47 years) eligible for the ovarian cancer analysis, and 2213 women (median age, 47 years; IQR, 40-55 years) eligible for the contralateral breast cancer analysis, 426 were diagnosed with breast cancer, 109 with ovarian cancer, and 245 with contralateral breast cancer during follow-up. The cumulative breast cancer risk to age 80 years was 72% (95% CI, 65%-79%) for BRCA1 and 69% (95% CI, 61%-77%) for BRCA2 carriers. Breast cancer incidences increased rapidly in early adulthood until ages 30 to 40 years for BRCA1 and until ages 40 to 50 years for BRCA2 carriers, then remained at a similar, constant incidence (20-30 per 1000 person-years) until age 80 years. The cumulative ovarian cancer risk to age 80 years was 44% (95% CI, 36%-53%) for BRCA1 and 17% (95% CI, 11%-25%) for BRCA2 carriers. For contralateral breast cancer, the cumulative risk 20 years after breast cancer diagnosis was 40% (95% CI, 35%-45%) for BRCA1 and 26% (95% CI, 20%-33%) for BRCA2 carriers (hazard ratio [HR] for comparing BRCA2 vs BRCA1, 0.62; 95% CI, 0.47-0.82; P=.001 for difference). Breast cancer risk increased with increasing number of first- and second-degree relatives diagnosed as having breast cancer for both BRCA1 (HR for ≥2 vs 0 affected relatives, 1.99; 95% CI, 1.41-2.82; P<.001 for trend) and BRCA2 carriers (HR, 1.91; 95% CI, 1.08-3.37; P=.02 for trend). Breast cancer risk was higher if mutations were located outside vs within the regions bounded by positions c.2282-c.4071 in BRCA1 (HR, 1.46; 95% CI, 1.11-1.93; P=.007) and c.2831-c.6401 in BRCA2 (HR, 1.93; 95% CI, 1.36-2.74; P<.001). Conclusions and Relevance These findings provide estimates of cancer risk based on BRCA1 and BRCA2 mutation carrier status using prospective data collection and demonstrate the potential importance of family history and mutation location in risk assessment.

CHEK2*1100delC homozygosity is associated with a high breast cancer risk in women

Background Mutations in the CHEK2 gene confer a moderately increased breast cancer risk. The risk for female carriers of the CHEK2*1100delC mutation is twofold increased. Breast cancer risk for carrier women is higher in a familial breast cancer setting which is due to coinheritance of additional genetic risk factors. This study investigated the occurrence of homozygosity for the CHEK2*1100delC allele among familial breast cancer cases and the associated breast cancer risk. Methods and results Homozygosity for the CHEK2*1100delC allele was identified in 8/2554 Dutch independent familial non-BRCA1/2 breast cancer cases. The genotype relative risk for breast cancer of homozygous and heterozygous familial breast cancer cases was 101.34 (95% CI 4.47 to 121 000) and 4.04 (95% CI 0.88 to 21.0), respectively. Female homozygotes appeared to have a greater than twofold increased breast cancer risk compared to familial CHEK2*1100delC heterozygotes (p=0.044). These results and the occurrence of multiple primary tumours in 7/10 homozygotes indicate a high cancer risk in homozygous women from non-BRCA1/2 families. Conclusions Intensive breast surveillance is therefore justified in these homozygous women. It is concluded that diagnostic testing for biallelic mutations in CHEK2 is indicated in non-BRCA1/2 breast cancer families, especially in populations with a relatively high prevalence of deleterious mutations in CHEK2.

Age- and Tumor Subtype–Specific Breast Cancer Risk Estimates for CHEK2*1100delC Carriers

PURPOSE CHEK2*1100delC is a well-established breast cancer risk variant that is most prevalent in European populations; however, there are limited data on risk of breast cancer by age and tumor subtype, which limits its usefulness in breast cancer risk prediction. We aimed to generate tumor subtype- and age-specific risk estimates by using data from the Breast Cancer Association Consortium, including 44,777 patients with breast cancer and 42,997 controls from 33 studies genotyped for CHEK2*1100delC. PATIENTS AND METHODS CHEK2*1100delC genotyping was mostly done by a custom Taqman assay. Breast cancer odds ratios (ORs) for CHEK2*1100delC carriers versus noncarriers were estimated by using logistic regression and adjusted for study (categorical) and age. Main analyses included patients with invasive breast cancer from population- and hospital-based studies. RESULTS Proportions of heterozygous CHEK2*1100delC carriers in controls, in patients with breast cancer from population- and hospital-based studies, and in patients with breast cancer from familial- and clinical genetics center-based studies were 0.5%, 1.3%, and 3.0%, respectively. The estimated OR for invasive breast cancer was 2.26 (95%CI, 1.90 to 2.69; P = 2.3 × 10(-20)). The OR was higher for estrogen receptor (ER)-positive disease (2.55 [95%CI, 2.10 to 3.10; P = 4.9 × 10(-21)]) than it was for ER-negative disease (1.32 [95%CI, 0.93 to 1.88; P = .12]; P interaction = 9.9 × 10(-4)). The OR significantly declined with attained age for breast cancer overall (P = .001) and for ER-positive tumors (P = .001). Estimated cumulative risks for development of ER-positive and ER-negative tumors by age 80 in CHEK2*1100delC carriers were 20% and 3%, respectively, compared with 9% and 2%, respectively, in the general population of the United Kingdom. CONCLUSION These CHEK2*1100delC breast cancer risk estimates provide a basis for incorporating CHEK2*1100delC into breast cancer risk prediction models and into guidelines for intensified screening and follow-up.

PALB2 analysis in BRCA2-like families

BRCA2 and PALB2 function together in the Fanconi anemia (FA)–Breast Cancer (BRCA) pathway. Mono-allelic and bi-allelic BRCA2 and PALB2 mutation carriers share many clinical characteristics. Mono-allelic germline mutations of BRCA2 and PALB2 are risk alleles of female breast cancer and have also been reported in familial pancreatic cancer, and bi-allelic mutations cause a severe form of Fanconi anemia. In view of these similarities, we investigated whether the prevalence of PALB2 mutations was increased in breast cancer families with the occurrence of BRCA2 associated tumours other than female breast cancer. PALB2 mutation analysis was performed in 110 non-BRCA1/2 cancer patients: (a) 53 ovarian cancer patients from female breast-and/or ovarian cancer families; (b) 45 breast cancer patients with a first or second degree relative with pancreatic cancer; and (c) 12 male breast cancer patients from female breast cancer families. One truncating PALB2 mutation, c.509_510delGA, resulting in p.Arg170X, was found in a male breast cancer patient. We conclude that germline mutations of PALB2 do not significantly contribute to cancer risk in non-BRCA1/2 cancer families with at least one patient with ovarian cancer, male breast cancer, and/or pancreatic cancer.

Lack of large genomic deletions in BRIP1, PALB2, and FANCD2 genes in BRCA1/2 negative familial breast cancer.

16% of the familial BC cases [2]. Other BC sus-ceptibility genes include TP53 [16], PTEN [15], ATM [24],LKB1/STK11 [8], CHEK2 [28], BRIP1/FANCJ [27], andPALB2/FANCN [22]. However to date, the majority offamilial BC cases can not be attributed to mutations in oneof the known susceptibility genes.The discovery of the breast cancer susceptibility geneBRCA2asthegenedefectiveintheFanconianemia(FA)-D1complementation group [11], the identification of BRIP1(BRCA1 InteractingProtein)[3, 12,13] andPALB2 (PartnerAnd Localizer of BRCA2) [23, 32] as the genes responsiblefor the FA-J and FA-N complementation groups, respec-tively, established a clear link between breast cancer sus-ceptibility and FA. Fanconi anemia (FA) is a recessivelyinherited chromosomal instability syndrome with autosomalor X-linked mode of inheritance, and is characterized by anincreased susceptibility to several forms of malignancies [1,17].Thediseaseiscausedbymutationsinoneofthe13genesso far identified [18]. The FA gene products interact in acommon pathway whereby most of the proteins (FANCA, -B, -C, -E, -F, -G, -L, and -M) form a multiprotein complexthat is required for the monoubiquitination of FANCD2 andFANCI.However,thismodificationstepisnotinfluencedbyFANCD1(BRCA2),FANCJ(BRIP1),orFANCN(PALB2),and hence these proteins seem to act downstream of thisprocess. FANCD2 and FANCI are thought to form a proteincomplex (ID complex), which translocates to DNA damagesites where it co-localizes with the downstream FA proteins,BRCA2/FANCD1, BRIP1/FANCJ, and PALB2/FANCNand other proteins that are involved in the recognition andrepair of DNA damage, such as BRCA1, ATM, NBS, andRAD51 [31].Several studies explored whether heterozygous femalecarriers for a mutation in one of the FA genes are atincreased risk for breast cancer. To date, only mutations inthe ‘‘downstream’’ FA genes have been found to signifi-cantly elevate the risk of developing breast cancer. Het-erozygous mutations in BRIP1/FANCJ and PALB2/FANCNappear to increase the risk 2- and 2.3-fold, respectively [22,27]. Risk assessment has been based on screening fortruncating mutations in these genes in familial breastcancer (FBC) patients lacking mutations in BRCA1/2.Furthermore, FANCD2 mutations, have been suggested toplay a role in the development of breast cancer based onobservations of Fancd2 knockout mice, which demon-strated a high incidence of epithelial tumors, includingmammary and ovarian tumors [10]. However, in humans asignificant contribution of FANCD2 mutations to FBCcould not be established [14, 26].

Analysis of the novel fanconi anemia gene SLX4/FANCP in familial breast cancer cases.

SLX4/FANCP is a recently discovered novel disease gene for Fanconi anemia (FA), a rare recessive disorder characterized by chromosomal instability and increased cancer susceptibility. Three of the 15 FA genes are breast cancer susceptibility genes in heterozygous mutation carriers—BRCA2, PALB2, and BRIP1. To investigate if defects in SLX4 also predispose to breast cancer, the gene was sequenced in a cohort of 729 BRCA1/BRCA2‐negative familial breast cancer cases. We identified a single splice site mutation (c.2013+2T>A), which causes a frameshift by skipping of exon 8. We also identified 39 missense variants, four of which were selected for functional testing in a Mitomycin C‐induced growth inhibition assay, and appeared indistinguishable from wild type. Although this is the first study that describes a truncating SLX4 mutation in breast cancer patients, our data indicate that germline mutations in SLX4 are very rare and are unlikely to make a significant contribution to familial breast cancer.

Outcome of BRCA1- compared with BRCA2-associated ovarian cancer: a nationwide study in the Netherlands

BACKGROUND Recent studies suggested an improved overall survival (OS) for BRCA2- versus BRCA1-associated epithelial ovarian cancer (EOC), whereas the impact of chemotherapy is not yet clear. In a nationwide cohort, we examined the results of primary treatment, progression-free survival (PFS), treatment-free interval (TFI), and OS of BRCA1 versus BRCA2 EOC patients. METHODS Two hundred and forty-five BRCA1- and 99 BRCA2-associated EOC patients were identified through all Dutch university hospitals. Analyses were carried out with the Pearsons Chi-square test, Kaplan-Meier, and Cox regression methods. RESULTS BRCA1 patients were younger at EOC diagnosis than BRCA2 patients (51 versus 55 years; P < 0.001), without differences regarding histology, tumor grade, and International Federation of Gynecology and Obstetrics (FIGO) stage. Complete response rates after primary treatment, including chemotherapy, did not differ between BRCA1 (86%) and BRCA2 patients (90%). BRCA1 versus BRCA2 patients had a shorter PFS (median 2.2 versus 3.9 years, respectively; P = 0.006), TFI (median 1.7 versus 2.8 years; P = 0.009), and OS (median 6.0 versus 9.7 years; P = 0.04). Differences could not be explained by age at diagnosis, FIGO stage or type of treatment. CONCLUSIONS PFS and OS were substantially longer in BRCA2- than in BRCA1-associated EOC patients. While response rates after primary treatment were similarly high in both groups, TFI, as surrogate for chemosensitivity, was significantly longer in BRCA2 patients.

Excess breast cancer risk in first degree relatives of CHEK2∗1100delC positive familial breast cancer cases

AIM The CHEK2∗1100delC mutation confers a relative risk of two for breast cancer (BC) in the general population. This study aims to explore the excess cancer risk due to the CHEK2∗1100delC mutation within a familial non-BRCA1/2 breast cancer setting. PATIENTS AND METHODS Cancer incidences were compared between first degree relatives of 107 familial breast cancer patients positive for the CHEK2∗1100delC mutation (CHEK2 positive families) and first degree relatives of 314 familial breast cancer patients without the CHEK2∗1100delC mutation (CHEK2 negative families). All families were derived from the same pool of familial non-BRCA1/2 breast cancer families (n=2554). Medical information of 2188 first degree relatives of these families was analysed for cancer risk. CHEK2∗1100delC status of relatives was unknown. RESULTS Increased breast cancer risk (hazard ratio (HR) 2.0 (95% confidence interval (CI): 1.4-2.7), p<0.001) was observed in sisters of CHEK2∗1100delC positive index cases compared to sisters of CHEK2∗1100delC negative index cases. HR was 1.6 (95% CI: 1.0-2.4) for mothers of CHEK2 positive versus negative index cases (p=0.041). For second primary breast cancers HR was increased in CHEK2∗1100delC positive index cases (HR 2.1, 95% CI: 1.3-3.3, p=0.003) and their sisters (HR 2.6, 95% CI: 1.1-6.1, p=0.025). CONCLUSION There is an excess breast cancer risk in first degree relatives of CHEK2∗1100delC positive non-BRCA1/2 familial breast cancer patients compared to non-CHEK2∗1100delC familial breast cancer relatives. Genotyping for the CHEK2∗1100delC mutation in a familial breast cancer setting contributes to optimal clinical surveillance in countries in which this mutation is prevalent. Carriers and female relatives are eligible for stringent breast surveillance programs.

Optimal age to start preventive measures in women with BRCA1/2 mutations or high familial breast cancer risk

Women from high‐risk families consider preventive measures for breast cancer including screening. Guidelines on screening differ considerably regarding starting age. We investigated whether age at diagnosis in affected relatives is predictive for age at diagnosis. We analyzed the age of breast cancer detection of 1,304 first‐ and second‐degree relatives of 314 BRCA1, 164 BRCA2 and 244 high‐risk participants of the Dutch MRI‐SCreening study. The within‐ and between‐family variance in the relatives age at diagnosis was analyzed with a random effect linear regression model. We compared the starting age of screening based on risk‐group (25 years for BRCA1, 30 years for BRCA2 and 35 years for familial risk), on family history, and on the model, which combines both. The findings were validated in 63 families from the UK‐MARIBS study. Mean age at diagnosis in the relatives varied between families; 95% range of mean family ages was 35–55 in BRCA1‐, 41–57 in BRCA2‐ and 44–60 in high‐risk families. In all, 14% of the variance in age at diagnosis, in BRCA1 even 23%, was explained by family history, 7% by risk group. Determining start of screening based on the model and on risk‐group gave similar results in terms of cancers missed and years of screening. The approach based on familial history only, missed more cancers and required more screening years in both the Dutch and the United Kingdom data sets. Age at breast cancer diagnosis is partly dependent on family history which may assist planning starting age for preventive measures.

A novel splice site mutation in the noncoding region of BRCA2: implications for Fanconi anemia and familial breast cancer diagnostics.

Fanconi anemia (FA) is a rare recessive disorder with chromosomal instability, congenital abnormalities, and a high cancer risk. The breast cancer susceptibility gene BRCA2 (FANCD1) is one of the 16 genes involved in this recessive disease. We have identified a novel mutation of the splice donor site of intron 1 in the noncoding region of BRCA2 in a Japanese FA family. This mutation may account for the FA phenotype in a patient originally reported to have biallelic mutations in BRCA2. Subsequent functional studies revealed that one of the mutations, K2729N, was a neutral change. As reported here, a more careful analysis resulted in the identification of a novel splice site mutation. Functional analysis using a mouse embryonic stem cell‐based assay revealed that it causes aberrant splicing, reduced transcript levels and hypersensitivity to DNA damaging agents, suggesting that it is likely to be pathogenic. Although similar pathogenic variants in the noncoding region of BRCA1 and 2 were not identified in a cohort of 752 familial breast cancer cases, we still think this finding is relevant for mutation analysis in Hereditary Breast and Ovarian Cancer Syndrome families in a diagnostic setting.