BRCA1/BRCA2 mutations in Japanese women with ductal carcinoma in situ

1 INTRODUCTION

Since 1996, breast cancer has become the most frequent malignancy in women in Japan and estimates of new cases in 2016 were 90,000 according to National Cancer Center of Japan. Widespread adoption of screening increases breast cancer incidence in a given population and changes the characteristics of cancers detected, with increased incidence of lower-risk cancers, premalignant lesions, and ductal carcinoma in situ (DCIS). Although DCIS is not immediately life-threatening, it is associated with an increased risk of invasive breast cancer (IBC). Pathologists agree that DCIS is a preneoplastic lesion, and shares certain features with IBC such as genetic signature and epidemiologic risk factors (Fujii, Szumel, Marsh, Zhou, & Gabrielson, 1996; Hwang et al., 2004; O'Connell et al., 1998).

The identification of deleterious mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 has important implications for mutation carriers in general, because they are the principal cause of Hereditary Breast and/or Ovarian Cancer Syndrome (Miki et al., 1994; Wooster et al., 1995). Of all women with breast cancer, 5% to 10% may have a germline mutation of the genes BRCA1 and BRCA2 (Blackwood & Weber, 1998). The estimated lifetime risk of developing breast cancer for women with BRCA1 and BRCA2 mutations is 40% to 85%. Mutation carriers with a history of breast cancer have an increased risk of contralateral disease that may be as high as 5% per year (Frank et al., 1998). Mutations in either the BRCA1 or the BRCA2 gene also confer an increased risk of ovarian cancer (Easton et al., 1999; Ford, Easton, Bishop, Narod, & Goldgar, 1994) or other primary cancers (Easton et al., 1999; Ford et al., 1994). When BRCA1/BRCA2 mutation carriers were diagnosed before age 40 years, the risk of a contralateral breast cancer (CBC) reached nearly 50% in the ensuing 25 years (Garber & Golshan, 2009; Graeser et al., 2009).

The association of BRCA mutations with IBC is well established. DCIS is now considered a component of the BRCA mutation clinical spectrum (Bayraktar et al., 2012; Hall, Reid, & Wenstrup, 2010; Hwang et al., 2007; Smith et al., 2007). A few retrospective studies have examined the prevalence of BRCA1/BRCA2 mutations in women diagnosed with DCIS and have reported mutation rates ranging between 3.3% (Claus, Petruzella, Matloff, & Carter, 2005) and 13% (Frank et al., 2002; Hall, Reid, & Wenstrup, 2010). Those studies support the concept that women with DCIS, like their counterparts with IBC, warrant genetic risk assessment and testing on the basis of high-risk variables. Notably, the knowledge of a BRCA1/BRCA2 mutation is likely to significantly change the assessment of a DCIS patient's risks for future cancers and the cancer prevention/risk reduction recommendations that would be considered. Subsequent studies have led to the suggestion that the preinvasive phase may be shortened or even absent in hereditary breast cancers, particularly those associated with BRCA1 mutations (Jacquemler, Eisinger, Guinebretiere, Stoppa-Lyonnet, & Sobol, 1996). But patients in studies above are almost from US and other Western countries, while only a few reports have been published concerning the prevalence of BRCA1/BRCA2 mutations with DCIS among Japanese people (Ikeda et al., 2001; Kawahara et al., 2004; Noguchi et al., 1999; Sekine et al., 2001).

The purpose of our study is to further characterize the association between DCIS and BRCA mutations in Japanese women and to provide the genetic basis for directing the treatment and predicting prognosis for DCIS women with BRCA1/BRCA2 mutation. We also hope to find special independent predictors for BRCA mutation in DCIS and could recommend genetic counseling and testing for Japanese patients with DCIS of high risk of BRCA mutation.

2 MATERIALS AND METHODS

3 RESULTS

4 DISCUSSION

In our study, it indicated an overall 18.4% (17.6% before age 50 years) prevalence of deleterious BRCA1/BRCA2 mutations in high-risk women diagnosed with DCIS, supporting the presence of an in situ phase of carcinogenesis in the development of at least some BRCA-associated breast cancer (Arun et al., 2009). One study evaluated the mutation rate in 10,000 consecutive patients who were referred for genetic testing in Myriad Genetic Laboratories (Frank et al., 2002). The prevalence of BRCA mutations was 13% in women who had DCIS diagnosed before age 50 years versus 24% in women who had IBC. Hall et al. (2010) conducted a cross-sectional analysis of the Myriad Genetics BRCA1/BRCA2 database and reported an overall 5.9% prevalence of BRCA1/BRCA2 mutations in non-AJ patients with carcinoma in situ (CIS) (ductal or lobular). But only a few studies published have described the prevalence of BRCA mutation status in Japanese women with DCIS. Among mutations detected in BRCA1, L63X, and Q934X were reported as founder mutation in Japanese (Ikeda et al., 2001; Lakhani, Easton, & Stratton, 1997; Sekine et al., 2001; Sugano et al., 2008). In our study, Q1721X (c.5280C>T) was detected in only one subject, which has not previously reported nor been listed in the BIC database. Genetic variants of unknown significance G401E (1321G>A) were detected in one subject and also was thus far unreported in the BIC database. In the analysis of BRCA2, Ikeda et al. (2001) showed that BRCA2 5802delTTAA mutation was considered as common in Japanese breast cancer patients, and Nakamura et al. (Lakhani et al., 1997) reported 5804del4 and R3128X was most frequent mutation. In our study, S2835X, 3036del4, 1506delA, R2318X, I2675V, and 8817insA had been reported in Japanese (Nakamura et al., 2015). K467X (c.1627A>T) was previously reported in a Korean population (Kang et al., 2002), and it's the first time to be detected in a Japanese subject in our study. E1299X (c.4123G>T) was a novel mutational type which was detected in an age 70 years Japanese DCIS patient with luminal B subtype. As for genetic variants of uncertain significance, two mutational types H3056Y (c.9394C>T) and IVS6–2A>G were detected once in our study which were far unreported in the BIC database. IVS6–2A>G had been reported in Japanese (Lakhani et al., 1997), H3056Y (c.9394C>T) was novel mutational type in Japanese. But we did not detect most frequent type of BRCA1/2 mutation in our cohort, the reason is perhaps that DCIS is less commonly in breast cancer, a large-scale cohort study is required to obtain more precise information about founder mutations of DCIS patients in Japan.

In our study, cohort of women with pure DCIS who were referred for genetic risk assessment, we identified the predictive factors for BRCA1/BRCA2 mutations. Multivariate analysis revealed that ≥2 family members with BC (OR, 5.242) was one of independent predictors for mutation status. Several studies (Frank et al., 1998; Smith et al., 2007; Claus et al., 2005; Hall et al., 2010) have identified an FH of OC and early onset BC as risk factors for BRCA mutations among DCIS probands. We found that FH of BC was related to BRCA mutation in univariate analyses (p = 0.042), but the association failed to reach statistical significance in multivariate analysis, and FH of OC has no relationship with BRCA mutation. Hall et al. 2010 determined that women who had early onset DCIS had a significantly increased risk of BRCA1/BRCA2 mutation compared with women who had late-onset disease (aged ≥50 years; OR, 1.5; 95% CI 1.1–2.1). This association was higher in women with very early onset disease (age <40 years vs. ≥40 years; OR, 1.8; 95% CI 1.3–2.3). Conversely, Smith et al. (2007) observed similar mutation rates between patients with DCIS who were diagnosed at age <50 years and with those who were diagnosed at a later age. In our study, the BRCA mutation rate was significantly higher in patients who were younger than 35 years (p = 0.046), but it was also predictive of mutation status in multivariate analysis (OR 0.149, 95% CI 0.023–0.954, p = 0.045). ER status, PR status, HER2 status, and Ki67 index (cut off by 14% or 30%) did not differ between BRCA mutation carriers and noncarriers. But subgroup analysis showed that ER+/HER2+ status (OR 5.034, 95% CI 1.092–23.210, p = 0.038) remained as a significant predictor for BRCA mutation. So it's suggested that DCIS patients with total relatives with BC DX ≥2, age at diagnosis ≤35 years and ER+/HER+ status have high risk of BRCA mutation and could be recommended to receive genetic counseling and BRCA testing.

BRCA1 tumors are more frequently poorly differentiated (grade 3) carcinomas. The proportion of grade 3 carcinomas ranged from 66% to 100% in different series, (Eerola et al., 2005; Lakhani et al., 1997; Lynch, Holden, Buys, Neuhausen, & Gaffney, 1998) while the proportion of grade 3 tumors in age-matched sporadic tumors ranged from 15% to 55% (Agnarsson et al., 1998; Eerola et al., 2005; Lakhani et al., 1997, 2000 ; Lynch et al., 1998). In our study, there's only 1 BRCA1 mutation, it has Grade 3, TN subtype and higher proliferation (ki67 > 14%). It perhaps indicated that DCIS occurring in carriers of BRCA1 mutations are also more likely to be ER-negative, PR-negative, HER2 receptor-negative, and have a basal phenotype.

BRCA2 tumors are more frequently moderately or poorly differentiated carcinomas (grades 2 and 3) (Agnarsson et al., 1998; Lakhani et al., 1997, 2000 ; Lynch et al., 1998). In our study, no significant differences were found in grade between BRCA2 carriers and noncarriers (p = 0.319). But it's found that BRCA2 carriers are much higher in Grade 2 and 3 compared to that of BRCA2 noncarriers. It's similar to BRCA2 carriers in invasive carcinomas. In BRCA2 tumors, in contrast to BRCA1 tumors, it has been shown that the percentage of ER-positive cases. Foulkes et al. (2004) analyzing tumors from BRCA2 positive patients <45 years, found a statistically significant difference in the percentage of ER-positive tumors among BRCA2 carriers and noncarriers. The percentage of ER-positive tumors was higher in BRCA2 tumors; however, there was no difference found in a subanalysis of tumors from patients >55 years. Our data indicated that BRCA2 carriers with DCIS were tend to be ER-positive (p = 0.042) no matter with the age of patients, and subgroup analysis showed BRCA2 tumors with DICS was higher in expression of ER+/PR+ (p = 0.049). Data on HER2 expression in BRCA2-associated tumors vary from series to series, probably as a consequence of differences in the techniques employed. We found no significant difference between HER2 status and BRCA2 mutation, but subgroup analysis suggested that ER+/HER2+ could be an independent risk factor for BRCA2 mutation, and it's also one of independent predictive factors for BRCA mutation in our study. Since BRCA2 has a major role in DNA repair, its suppression is thought to induce unrepaired DNA lesions, which cause cell cycle arrest by activating checkpoint signaling. So we also found BRCA2 carriers with DCIS were tend to be lower proliferation (<30%), whereas has no significant difference.

The proportion of DCIS among surgically resected breast cancers is reported to be 20% in Western countries and nearly 10% in Japan (Burstein, Poluak, Wong, Lester, & Kaelin, 2004; Cancer Statistics in Japan, 2013; Ernster et al., 2003). Pure DCIS in itself is not a life-threatening disease, and the local recurrences if that appear as DCIS do not influence the overall survival rate of patients. True DCIS will theoretically not metastasize to regional lymph nodes or relapse in a distant organ, and thus the management of DCIS patients focuses on local control of the primary lesion and early detection and treatment of both IBTR and CBTR (Fisher et al., 2002, 1999 ). BRCA1/BRCA2 mutations have been shown to indicate a higher susceptibility to develop BC. Individuals who carry one of these mutations have a 43%–84% risk of developing BC, and up to a 65% risk for CBC (Finkelstein et al., 2006; Ford et al., 1998). But in our study, BRCA mutation status was not associated significantly with occurrence of IBTR. It indicated that, BCS might be a treatment option for DCIS patients with BRCA mutation, for they may be more sensitive to radiation (Garcia-Etienne et al., 2009; Kirova et al., 2010). But we need additional data of more research samples to support this conclusion. It's also found that CBTR rate was higher or tended to be higher in DCIS patients with ER negative, but no relationship with BRCA mutation status. Further study was needed to discuss whether BRCA mutation is the independent factor for CBTR in DCIS patients, and it's very important for DCIS women with BRCA mutation whether or not to choose contralateral prophylactic mastectomy.

5 CONCLUSION

DCIS is equally as prevalent in patients who were BRCA mutation carriers as in high familial-risk women who were noncarriers, but occurs at earlier age. BRCA2 carriers have higher incidence in DCIS than that of BRCA1 carriers, and tend to be higher grade and more frequently ER positive and lower proliferation. Total relatives with BC DX ≥2, age at diagnosis ≤35 years and ER+/HER2+ might be independent predictors for BRCA mutation in Japanese women with DCIS and patients of these risk factors should be recommended to receive genetic counseling and BRCA testing.

CONFLICT OF INTEREST

None declared.