BRCA1/2 Mutation Testing Among Adult Women With HER2-Negative Advanced Breast Cancer: Results From a Multi-Country, Real-World Study

Purpose: We assessed real-world patient demographics and breast cancer susceptibility genes 1 or 2 (BRCA1/2) mutation testing rates among adult women with human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ABC). Methods: Oncologists across the US and EU5 abstracted data from medical charts for 8–10 consecutive adult women presenting with HER2-negative ABC in 2015 and 2017. BRCA1/2 mutation (germline and/or somatic) testing was analysed overall and stratied by factors: region; year of data collection; hormone receptor (HR) status; age group; practice setting. Results: Records on 6161 adult women with HER2-negative ABC were provided by 742 oncologists. Overall, 28% of women with ABC received BRCA1/2 mutation testing. Compared with patients tested for BRCA1/2 mutations, untested patients were more likely to be aged ≥ 45 years, have HR-positive/HER2-negative ABC, have no known family history of breast/ovarian cancer, and be postmenopausal (all P < 0.0001). BRCA1/2 mutation testing rates were signicantly lower in the EU5 versus US (21% vs 50%; P < 0.0001). Signicantly lower BRCA1/2 testing rates were observed in women aged ≥ 45 versus <45 years, women without versus with a known family history of breast/ovarian cancer and women with HR-positive/HER2-negative ABC versus advanced TNBC (all P < 0.0001). Conclusions: BRCA1/2 mutation testing rates were low, and disparities were observed in demographics and clinical characteristics among patients who received a BRCA1/2 mutation test versus untested patients. Consistent with updated international guidelines, opportunities exist to increase BRCA1/2 mutation testing, particularly in patients aged ≥ 45 years, with HR-positive/HER2-negative ABC, or without a known family history of breast/ovarian cancer. rates were observed Age ≥ 45 years, no family history and HR-positive were linked to lower testing rates exist to increase BRCA1/2 mutation testing as per updated guidelines


Introduction
Mutations in breast cancer susceptibility genes 1 or 2 (BRCA1/2) are associated with an increased risk of developing breast and ovarian cancers, and have been linked to other tumor types, including ovarian, prostate and pancreatic cancer [1][2][3]. In the US and Europe, treatment recommendations and guidelines for human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ABC) include both non-targeted (e.g., platinum-based chemotherapy) and targeted therapies for germline BRCA1/2-associated ABC [4][5][6]. Recently, two poly(ADP-ribose) polymerase (PARP) inhibitors, talazoparib and olaparib, demonstrated signi cant improvements in progression-free survival, a manageable adverse-event pro le, and favourable patient-reported outcomes compared with physician's choice of chemotherapy in two randomised Phase III trials [7,8]. Both agents have been approved in the US and Europe as monotherapy for the treatment of patients with deleterious or suspected deleterious germline BRCA1/2-mutated HER2-negative locally advanced and/or metastatic breast cancer [9][10][11][12][13][14]. Consensus guidelines on genetic screening for breast cancer (BC) were subsequently expanded to re ect the clinical utility of germline BRCA1/2 mutation status for identifying candidates for PARP inhibitor therapy and platinum agents [4,5,15,16].
In addition to guiding treatment decisions, germline BRCA1/2 mutation testing can help identify familial risk and offer preventive measures to healthy relatives [17]. Identi cation of risk may also be important for early diagnosis of cancer, planning intensi ed local follow-up care of the breast, and, if necessary, initiation of prophylactic surgery [16,17]. In the prospective PRAEGNANT registry, 5.0% of patients with unselected ABC had a germline BRCA1/2 mutation regardless of family history [18], with germline BRCA1/2 mutations occurring more frequently in patients with triple-negative BC (TNBC) than in those with hormone receptor (HR)-positive disease [18,19]. Therefore, understanding BRCA1/2 mutation status has a substantial impact on oncological care.
Historically, rates of BRCA1/2 mutation testing among women with BC reported in the US and Europe have been low. According to a study linking data from a US Surveillance, Epidemiology, and End Results (SEER) registry with genetic testing results, only 24.1% of women diagnosed with BC between 2013 and 2014 had germline testing results for pathogenic variants, including BRCA1/2 [20]. For women with a personal history of BC meeting ≥ 1 speci c eligibility criterion, one study using pooled data sets from 2005, 2010 and 2015 found that 29.0% of patients discussed, 20.2% were advised to undergo, and 15.3% underwent genetic testing for cancer risk [21]. Another US study reported that 16.7% of patients with metastatic BC diagnosed between 2011 and 2018 had germline testing results for BRCA1/2 mutations [22]. Limited published data are available for Europe, although the results of a study using abstracted data from medical charts in the US, the European Union (EU) 4 (France, Germany, Spain and Italy) and Israel found that germline BRCA1/2 mutation testing rates in patients with HER2-negative ABC in 2019/2020 were signi cantly lower in the EU4 than in the US and Israel (26% vs 45% [P = 0.0008] and vs 97% [P < 0.0001], respectively) [23]. Recently, consensus guidelines have expanded to recommend BRCA1/2 mutation screening [4,5,[15][16][17][24][25][26][27], and most oncologists in the US and Europe now have access to targeted treatments [23].
The current study assessed real-world BRCA1/2 (germline and/or somatic) mutation testing rates among adult women with HER2-negative ABC in the US and in France, Germany, Italy, Spain and the UK (EU5). The study used data collected in 2015 and 2017, and therefore provides historical baseline BRCA1/2 mutation testing rates before the US and EU approvals of olaparib and talazoparib for germline BRCA1/2-mutated HER2-negative locally advanced and/or metastatic BC [9,11,12], and predates some of the more recently expanded guidelines on genetic screening for BC [4, 5, 15-17, 24, 26, 27]. Therefore, the results of this study can be used as a baseline reference to monitor BRCA1/2 mutation testing rates.

Study design and population
Oncologists were recruited to abstract data from patient medical charts and complete patient record forms for adult women with HER2-negative ABC treated in the US and EU5. Data were abstracted from medical charts for the next 8-10 consecutive adult women presenting with HER2-negative ABC in 2015 and 2017. Oncologists were asked whether each patient had undergone any test for a germline and/or somatic BRCA1/2 mutation (information on the type of test, i.e., germline or somatic, was not collected). Data were collected in two waves (February to May 2015, and March to July 2017) and combined for common variables (region, HR status, age group, practice setting) where questions and answer categories were comparable across both years. Oncologists were reimbursed for their participation.
A geographically representative sample of oncologists was recruited, along with patients with ABC treated in routine clinical practice. Only oncologists treating patients with ABC were eligible. Oncologists were required to be actively involved in the prescribing decisions for patients with ABC (Stage IIIb/c-IV) and to consult with a minimum of three patients with ABC per week. Patient inclusion criteria included female sex, age ≥18 years at data collection, and histologically or cytologically con rmed ABC. Oncologists were asked to exclude records for patients involved in clinical trials.
Data were collected in such a way that patients and physicians could not be identi ed directly; all data were aggregated and de-identi ed before receipt. Data collection in the 2017 wave received ethical approval from the Freiburger Ethik-Kommission International and the Western Institutional Review Board.

Analysis methods
Testing for germline and/or somatic BRCA1/2 mutations was assessed for the overall cohort and strati ed by region (US vs EU5); region by year (2015 vs 2017); known family history of breast or ovarian cancer (yes vs no); region (US vs EU5), HR status (HR-positive/HER2-negative vs TNBC) and age groups (<45, 45-54, 55-64 and ≥65 years); known family history of breast or ovarian cancer by HR status and age group; and HR status, age group and practice setting (academic medical centre vs non-academic medical centre/community oncologist) by year. Differences in demographics and clinical characteristics among women who were tested or not tested for germline and/or somatic BRCA1/2 mutations were analysed using t tests for continuous variables and Fisher's exact test for categorical variables. Differences in BRCA1/2 mutation testing rates for the strati cation factors were analysed via Fisher's exact tests. Univariate logistic regression was used to evaluate the relationship between age and BRCA1/2 mutation testing; odds ratios of <1, 1 and >1 indicate lower, equal and higher odds of being tested, respectively, versus the reference value.

Patient demographics and clinical characteristics
Records on 6161 adult women with HER2-negative ABC were provided by 742 oncologists, with 1285 and 4876 records from the US and EU5, respectively.
Demographics and baseline clinical characteristics by BRCA1/2 mutation testing (tested vs not tested) for 2015 and 2017 combined are provided in Table 1, with comparisons (tested vs not tested) by region in the supplementary material (Table A.1). The mean age was 63.4 years (58.3 vs 65.4 years in tested vs not tested); 75% of women had HRpositive/HER2-negative ABC, 23% had advanced TNBC and 2% had unknown HR status ABC. Women who were not tested for BRCA1/2 mutation were more likely to have HR-positive/HER2-negative ABC, have no known family history of breast or ovarian cancer, be postmenopausal, and be currently unemployed versus women who were tested (all P < 0.0001).
Lower BRCA1/2 mutation testing rates were generally observed in women with HR-positive/HER2-negative ABC versus those with TNBC, regardless of age, year, or region (Fig. 2). By year and region, the ndings among all ages combined were consistent with the overall results, with signi cantly lower BRCA1/2 mutation testing rates in women with HRpositive/HER2-negative ABC versus those with TNBC.
Women aged ≥ 45 years were less likely to have received BRCA1/2 mutation testing than women aged < 45 years ( Table 2). This was observed among women with HR-positive/HER2-negative ABC, as well as among women with advanced TNBC, and in both regions.
Lower BRCA1/2 mutation testing rates were also observed among women without versus with a known family history of breast or ovarian cancer (Fig. 3). This nding was consistent among different age groups with the exception of women with TNBC aged ≥ 65 years (Fig. 3). Similarly, this nding was consistent across both regions with the exception of US women with TNBC (Fig. 3).
By physician practice setting, signi cantly fewer patients with HR-positive/HER2-negative ABC underwent BRCA1/2 mutation testing at academic centres than in non-academic settings (P < 0.0001; Fig. 4). In contrast, for patients with TNBC, BRCA1/2 mutation testing rates were similar across both settings (Fig. 4).

Discussion
This study assessed real-world patient demographics and BRCA1/2 mutation testing rates in 2015 and 2017 in over 6000 adult women with HER2-negative ABC in the US and EU5. Overall, the rate of BRCA1/2 mutation testing in this study was low (28%); testing was signi cantly less frequent in the EU5 than in the US across both years. For both regions, the proportion of women with HER2-negative ABC who received BRCA1/2 mutation testing declined signi cantly from 2015 to 2017. This decrease may have been due to the approval of cyclin-dependent kinase (CDK)4/6 inhibitors, which became a new standard in combination with endocrine therapy during this same time period (starting in 2015/2016). Although CDK4/6 inhibitors can be used regardless of BRCA1/2 mutation status, optimal sequencing of PARP inhibitors (which were not available when this study was conducted) and CDK4/6 inhibitors has not been established in patients with BRCA1/2-mutated ABC [4,28].
The lower rates of BRCA1/2 mutation testing among women aged ≥ 45 years, those with HR-positive/HER2-negative ABC and those without a known family history of breast or ovarian cancer are consistent with the known risk factors for BRCA1/2 mutations [29,30]. While many physicians may be aware of the higher risk groups, it is important to consider other patient populations, such as those with HR-positive/HER2-negative ABC. Only 23% of women with HRpositive/HER2-negative ABC underwent BRCA1/2 mutation testing, compared with 41% of patients with TNBC. The rate of BRCA1/2 mutation testing among adult women with HR-positive/HER2-negative ABC was much lower in the EU5 than in the US, and was particularly low (16%) among women with HR-positive/HER2-negative ABC in the EU5 without a known family history of these BRCA1/2 mutation-related cancers. While germline BRCA1/2 mutations are more common in patients with TNBC (~ 10-15% of unselected patients), they also occur in approximately 5% of unselected patients with HR-positive/HER2-negative ABC [18, 19,29]. Moreover, because HR-positive BC accounts for 70-80% of all BC cases [31], it follows that numerically more patients with a BRCA1/2 mutation have HR-positive BC than TNBC. Increasing BRCA1/2 mutation testing in this population is therefore an important and clinically meaningful consideration, particularly for patients without a known family history of breast or ovarian cancer, due to the lack of awareness for this patient group. BRCA1/2 mutation testing rates were largely similar between academic and non-academic settings for patients with TNBC, although a surprisingly lower rate of testing was observed in academic versus non-academic centres for the HRpositive/HER2-negative population. A recent study found that germline BRCA1/2 mutation testing rates were signi cantly lower among oncologists in community practice than among those at academic medical centres [23]. Our results likely re ect the fact that oncologists were asked to exclude patients who were enrolled in clinical trials from the data they abstracted for this study, which may have caused bias in the data collected from academic centres.
Consistent with other studies [20][21][22], the overall BRCA1/2 mutation testing rates observed in this study were low, indicating suboptimal uptake of BRCA1/2 mutation testing. Although the European Society for Medical Oncology guidelines available in 2015 and 2017 encouraged genetic testing and counselling to explore the possibility of hereditary BC [17,24,25], low uptake of BRCA1/2 mutation testing in the EU5 was identi ed even among patients with a known family history of breast and/or ovarian cancer. Additionally, the varying rates of BRCA1/2 mutation testing across the US and EU5 and across the individual European countries is likely the result of different healthcare systems, local guidelines and policies. Therefore, there is a need to improve rates of BRCA1/2 mutation testing through focused education about genetic risk, incidences of mutations in metastatic BC, testing pathways, reimbursement of testing, and availability and e cacy of PARP inhibitors. Increased awareness of recent guideline recommendations, especially following the approval and availability of targeted therapies, should also help to improve BRCA1/2 mutation testing rates. It is possible that the disparity in BRCA1/2 mutation testing rates between the US and EU5, and across the individual European countries is likely the result of different healthcare systems, local guidelines, policies, and renumeration aspects. A systematic review of international guidelines on screening and management of BRCA-mutant BC published between January 2007 and February 2018 identi ed regional and organisational differences regarding genetic screening, counselling and treatment of BRCA1/2-mutant BC [32]. Genetic testing guidelines have also evolved over time, with more recent guidelines advocating broader criteria regarding family history [32]. Overall, a greater consensus and harmonisation of guidelines across geographic regions may help to optimise identi cation and management of patients with HER2-negative BC harbouring BRCA1/2 mutations [32].
Another development that might positively affect BRCA1/2 mutation testing rates is the availability of next-generation sequencing, which enables simultaneous sequencing of multiple cancer susceptibility genes and may be more e cient, faster and less expensive than testing for individual genes [33]. A recent cost-effectiveness analysis found that, compared with BRCA1/2 mutation testing based on clinical criteria or family history, multigene testing of BRCA1/2 and PALB2 in unselected patients with BC could reduce BC incidence and mortality, and would be cost-effective for UK and US healthcare systems [34]. Although the diagnostic and prognostic implications for many genes on existing multigene panels are not yet clear [4,35], the potential for simultaneous detection of pathogenic variants other than BRCA1/2 may in uence future uptake of genetic testing.
Key strengths of this study are that it included a relatively large sample (> 6000) of unselected patients treated in realworld clinical practice and captured data from multiple countries and across two distinct time periods. Analysis of patient demographics also allowed evaluation of the relationship between age and BRCA1/2 mutation testing. Because patient charts were randomly sampled, this analysis likely accurately re ects BRCA1/2 mutation testing in selected US and EU5 patient populations. Nonetheless, the study has some limitations relating to the self-reported nature of the data, as no independent veri cation was possible. Accuracy of the collected data was dependent on reporting by the physician and patient, and recall bias or missing information may have existed. All data were anonymised and aggregated prior to analysis; therefore, it was not possible to prevent double counting of patients in 2015 and 2017. The study was also more likely to collect data on patients who consult their physician more frequently. Of note, data collection in 2015/2017 was conducted before the US and EU approvals of PARP inhibitors for BRCA1/2-mutated HER2negative ABC; thus, the therapeutic utility of BRCA1/2 mutation testing at the time was limited to informing patient eligibility for platinum-based chemotherapy, along with the aforementioned advantages for identi cation of familial risk, planning of intensi ed follow-up care and early detection of ovarian cancer [16,17,32,36,37]. It will therefore be interesting to evaluate patterns of BRCA1/2 mutation testing in the PARP inhibitor era to determine whether uptake is increasing following the availability of targeted treatments. Finally, BRCA1/2 mutation testing in the current study was not con ned to testing for germline BRCA1/2 mutations, and germline and somatic BRCA1/2 mutations were not differentiated; therefore, some reports may have been for somatic BRCA1/2 mutations. The therapeutic implications of somatic BRCA1/2 mutations are not clear, as PARP inhibitors are approved only for HER2-negative ABC harbouring germline BRCA1/2 mutations [4,10,11,13,14].
In summary, BRCA1/2 mutation testing rates were low in this study, and disparities in testing were observed, including between years (2015 vs 2017) and regions (US vs EU5). BRCA1/2 mutation testing rates also varied with certain demographic and baseline characteristics, including age, HR status and family history of breast or ovarian cancer, consistent with previous reports [20,30]. Opportunities exist to increase BRCA1/2 mutation testing in patients with ABC, regardless of physician setting and particularly among those with HR-positive/HER2-negative disease, patients aged ≥ which received nancial support from P zer for the development of this manuscript. Alexander Niyazov: employee of and owns stock in P zer Inc.

Availability of data and materials
Publication of study results was not contingent on the sponsor's approval or censorship of the manuscript.
All data that support the ndings of this study are the intellectual property of Adelphi Real World. All requests for access should be addressed directly to Katie Lewis at katie.lewis@adelphigroup.com.   BRCA1/2 mutation testing rates by known family history of breast or ovarian cancer, HR status, region and age in adult women with HER2-negative ABC.