Breast cancer gene (BRCA) testing can identify individuals who have a higher risk of developing breast or ovarian cancer. This genetic testing can inform patients of management and treatment decisions, such as personalized surveillance or risk reduction surgery [1]. This can also be important for managing family members who may benefit from genetic counseling or testing [2].

Recently, with the development of olaparib, a poly(ADP ribose) polymerase inhibitor, the significance of BRCA mutation testing is increasing. Breast cancer patients with a BRCA mutation and human epidermal growth factor receptor 2 (HER2)–negative status, who can benefit from olaparib, show a proportion of approximately 7% [3]. In metastatic breast cancer, olaparib monotherapy reduced the risk of disease progression or death by 42% compared to standard therapy [4]. In patients who received local treatment with adjuvant or neoadjuvant chemotherapy, olaparib was associated with an improvement in invasive disease-free survival or distant metastasis-free survival [5].

While BRCA testing can be beneficial for some patients, not all individuals with a family history of breast cancer or other risk factors may be eligible for or benefit from testing. Testing can be expensive and may not be accessible to all patients, although in Korea it is covered by national insurance [6]. In addition, genetic counseling, which is an important component of the testing process [7], is not always feasible due to limited personnel availability [8,9]. It is expected that there will be variations in genetic counseling practices depending on the hospital’s circumstances; therefore, it is necessary to identify the disparities in the implementation of genetic testing.

As management strategies for mutation carriers continue to evolve, the significance of BRCA testing is emphasized, and it is now more crucial than ever to comprehend how this testing is being utilized in the real world. In this study, we investigated the annual implementation of BRCA testing in South Korea using national insurance claims data and identified regional or temporal variations in testing.

We found that between 2010 and 2020, the frequency of BRCA testing in breast cancer patients undergoing surgery has continued to increase, especially in Seoul. BRCA testing ratios increased in all health care delivery system, and the ratio in tertiary hospitals reached a plateau in 2018. BRCA testing was performed more often among individuals who were younger, had health insurance, had no co-morbidity, operated in Seoul, operated in tertiary hospitals, and were more recent. The majority of patients who were diagnosed with breast cancer in Seoul (97.8%) underwent testing in Seoul. In contrast, in metropolitan areas and other regions, a significant number of cases moved to Seoul and underwent BRCA testing (22.9% and 29.2%, respectively).

To our knowledge, this is the first nationwide study to report the implementation of BRCA testing in real practice and provide data for a possible explanation of the testing patterns. Previous studies have also reported chronological increases in the number of BRCA tests; however, the number of cases was limited as it was conducted in a single institution [13]. While other studies included only patients from specific regions [14] or patients with specific private insurance [15], our study was able to account for regional differences within a nation and identify the factors that contribute to these differences.

There was a study from South Korea that reported major cities had more tests than rural areas [16]. Another study identified differences in the frequency of BRCA testing according to geographic locations in the United States [17]. Additionally, a study using the Employer-Sponsored Health Insurance in the United States found that nonmetropolitan areas had significantly fewer BRCA tests compared to metropolitan areas and had significantly fewer cases of receiving magnetic resonance imaging within 90 days or 1 year after testing [18]. In our study, we traced the location of breast cancer diagnosis and BRCA testing of patient. Although there were differences in testing ratios between regions, a significant number of patients from non-Seoul areas were assumed to have moved to Seoul for breast cancer treatment, suggesting that the low testing ratios in non-Seoul areas reported in previous studies may have been underestimated.

We determined the ratios for BRCA testing based on patients who underwent surgery. Most patients were expected to receive BRCA testing at the site where they were receiving treatment, rather than at the site where they received the breast cancer diagnosis, for the convenience of testing and of correlating the testing results with the surgical procedures or adjuvant therapy. Of the study patients who underwent BRCA testing, 92.1% underwent surgery. The proportion of breast cancer cases in which BRCA testing was performed but surgery was not performed was low (7.9%); therefore, there was no difficulty in observing the overall trend, and it was an appropriate method to compare BRCA testing behavior by region or health care delivery system.

We identified that a significant number of patients diagnosed with breast cancer in metropolitan cities or elsewhere moved to Seoul and received BRCA testing. There was a report stating that in 2017, 19.8% of breast cancer patients in regions outside of Seoul moved to Seoul for their initial treatment; furthermore, compared to patients aged 60 or older, those younger than 40 were 94% more likely to move to Seoul for their treatment [11]. BRCA test also showed the same trend, which is likely because the initial treatment site and the site where BRCA testing is conducted usually coincide. However, the low ratio of BRCA testing in patients treated outside of Seoul cannot be solely attributed to the migration of patients, as the testing ratio in non-Seoul patients was only slightly lower than that in Seoul. While genetic counseling is required for BRCA testing, it is currently not covered by Korea’s national insurance. In one study, 55.6% of respondents in a professional survey said that financial burden was a challenge in genetic counseling [19]. In our study, the testing ratio was low in patients with medical aid, suggesting that there are additional barriers beyond insurance for these patients, who are exempt from most of their medical expenses [20]. It is known that patients may decline genetic counseling for various reasons, including concerns about the future impact of test results, emotional repercussions for themselves and their families, and a low perceived risk of cancer [21-23]. It is possible that psychological factors are distributed differently depending on the region.

In Korea, the National Health Insurance has covered BRCA testing since 2008, and there have been several studies on BRCA in Koreans, such as the Korean Hereditary Breast Cancer (KOHBRA) study [24,25]. From May 2012, reimbursement indications were specified for breast cancer patients under the age of 40, those with a second-degree family history of breast or ovarian cancer, those with bilateral breast cancer, those with multiple organ cancer, as well as male breast cancer and ovarian cancer patients. From July 2020, the reimbursement criteria were expanded to include breast cancer patients aged 40 and triple-negative patients aged 60 years or younger. The criteria for determining family history have also been expanded to include breast cancer, ovarian cancer, male breast cancer, metastatic prostate cancer, and pancreatic cancer within the patient’s third-degree relatives. The definition of multiple organ cancer was specified as breast cancer combined with either ovarian cancer or pancreatic cancer [26]. In our study, the pattern of annual increase in BRCA testing ratio did not match the expansion of major expansions in insurance standards, suggesting that there are other factors contributing to the pattern.

Although olaparib was not included in South Korea’s national insurance system, it was approved by South Korea’s Ministry of Food and Drug Safety for the treatment of metastatic breast cancer in October 2019 [27], and as an adjuvant treatment for early breast cancer in February 2023 [28]. In our study, there were a certain number of patients in other regions who did not receive BRCA testing even in 2020. With the introduction of olaparib and the increasing importance of confirming BRCA mutations, patients with an indication for testing should be informed to aid in their decision-making.

Since this study utilized nationwide claims data, information regarding hormone receptor or HER2 status, family history, and bilaterality—aside from age—was not available among the national insurance reimbursement indications for BRCA testing. And our study didn’t include patients aged 40. However, age under 40 years alone was helpful in identifying trends in BRCA testing ratios among people with indications. The BRCA mutation can also be diagnosed through multigene panel testing [29], but it was not additionally included in the analysis, as it may overlap with standalone BRCA tests and could be captured in national claims data only since February 2018, which was nearly the end of our study period. Since the timing and location of BRCA testing for some patients were different from those of breast cancer diagnosis, we had to calculate the ratio, rather than the proportion or rate, of BRCA-tested patients to the total number of patients who underwent surgery. However, since it would be rare for the time of surgery and BRCA testing to be significantly different, there would be no disruption to the overall trend. Although we were able to identify the increases or decreases in the test ratio by region and hospital size, the specific cause could not be determined.

The frequency of BRCA testing has increased over time in all regions of Korea. Especially, Seoul showed a higher frequency of BRCA testing compared to those of metropolitan areas or other areas. Also, about one-quarter of patients diagnosed in metropolitan cities and other regions moved to Seoul for medical purposes and underwent BRCA testing.