In the present study, we found that both the number of RRSO and BRCA tests increased significantly after insurance part coverage was extended. The number of RRSO in the 21-month period after April 2020, when health insurance partly coverage was started, exceeded the 6-year period before coverage. The number of BRCA tests for diagnosing HBOC also increased. Figure 3 shows a notable difference in the HBOC/RRSO ratio between 2020 and 2021. This indicates that the decision for RRSO was not made as soon as the diagnosis of HBOC was confirmed. Breast cancer patients sometimes undergo BRCA testing to determine the surgical procedure. In the case of HBOC, total mastectomy is recommended. Therefore, patients tend to undergo BRCA testing prior to breast cancer surgery and then undergo RRSO once they are undergoing breast cancer treatment.

In Japan, for procedures covered by insurance, the co-payment is 30% of the total cost in principle. The cost of the BRCA testing is approximately 200,000 JPY (1,408 USD), so the co-payment is 60,000 JPY (422 USD), covered by insurance. In the case of laparoscopic RRSO (=LBSO), medical expenses are about 600,000 JPY (4,225 USD); thus, the co-payment is about 180,000 JPY (1,267 USD). However, actual co-payments were lower, from 59,900 (421 USD) to 85,877 JPY (604 USD), and the co-payment ratio was only 10-14% as these patients were covered by the High-cost Medical Expense Benefit system, which allows patients to limit the amount of co-payment to a fixed monthly amount by applying in advance. The maximum amount of the co-payment is determined according to the patient's age and income. This system only applies to medical expenses that are covered by insurance.

Our findings suggest that the increase in the number of RRSO and BRCA tests was due to the decrease in co-payment. This phenomenon can be explained by price elasticity (PE). PE is a measure of how much the consumption of a product or service changes with changes in price, which is expressed as the percent change in consumption for a 1% change in price.

$$\textrm=\frac/\textrm}/\textrm}=\frac\ \textrm\ \textrm\ \textrm\ \textrm\ \textrm\ \textrm\ \textrm}\ \textrm\ \textrm\ \textrm\ \textrm\ \textrm\ \textrm}$$

This tool is useful because it is a unitless measure and provides information about the nature of the product (necessity or luxury) and the relationship between the products (substitutes or complements): if the absolute value of PE is less than 1, it is considered price inelastic; if it is greater than 1, it is considered price elastic [10].

PE tends to center on -0.17 in health care [11]. This indicates that a 1% increase in price results in a 0.17% decrease in demand. In general, services in health care are considered to be price inelastic; thus, there is little decrease in demand due to price increases. However, preventive care and pharmacy benefits are among the medical services with larger PE. When the price of care increases, consumers are able to substitute away from preventive care toward other goods and services that promote health such as nutritional supplements and healthy foods. In addition, preventive medical services may be put off when the price of such care increases [11]. RRSO is preventive care; thus, it may have been treated as a luxury. For BRCA1/2 pathogenic variant carriers, the risk of ovarian cancer, which is known for its very poor prognosis, is high. Furthermore, reliable screening methods to detect early-stage ovarian cancer are unavailable [12]. Our findings suggest that RRSO should not be considered a luxury item because it can reliably reduce the risk of ovarian cancer.

Price has been reported to be an important factor for health care promoters. In a study conducted in Sudan, free use of health centers for malaria treatment at different levels of coverage (25%, 50%, and 75%) increased their use for the treatment of children to 63.6%, 32.3%, and 280.4%, respectively (PE was -2.5, -0.6, and -3.7, respectively) [13]. In 2004, German health authorities introduced a 50% co-payment for patients, in an effort to save the cost of in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Prior to that, 100% reimbursement was available for up to four IVF and ICSI cycles. After the co-payment increase, the number of IVF and ICSI cycles decreased by 53% [14]. In Korea, BRCA testing and RRSO have been covered under the Korean universal health insurance system since 2012, and the number of both procedures has been increasing every year. The expansion of insurance coverage is thought to be one of the factors for this increase [15].

In this study, the number of RRSO increased 5.4 times after the procedure was covered by insurance. RRSO decreased from 100% self-payment to 30%, and the PE was -7.7. Similarly, the PE of the BRCA testing was -5.8. The PE of both was quite high as PE is considered in absolute value and price declines are considered the main factor in high PE. In addition, the establishment of the Japanese Organization of Hereditary Breast and Ovarian Cancer (2016), the publication of the Guidebook for Diagnosis and Treatment of HBOC Syndrome (2017), and Guidelines for Diagnosis and Treatment of HBOC syndrome (2021) improved the understanding of breast surgeons, gynecologists, and other medical professionals. Moreover, breast cancer patients have access to more information about HBOC syndrome. Price is reported to be more likely to influence an individual's decision to receive treatment than the frequency of visits after receiving treatment [16]; thus, it may influence the decision to receive RRSO.

In Japan, all medical care for asymptomatic blood relatives of HBOC syndrome is not covered by insurance. The frequency of BRCA1/2 pathological variant in the general population in Japan is reported to be 0.21% [17], which is relatively high. In the future, we expect insurance coverage for medical care for asymptomatic blood relatives. Medical treatment of HBOC syndromes, such as hypertension and hyperlipidemia, is a preventive intervention; thus, we propose that it should be covered by insurance. Because, at present, ovarian cancer cannot be reliably detected in its early stages by screening. Several reports indicated that RRSO is more cost-effective than surveillance [18, 19]. In the U.S., health care coverage for the working-age population is provided primarily through private health insurance, with major insurance companies covering BRCA testing and RRSO. Because this is the least expensive method for managing the insured’s risk [20]. In addition, RRSO is covered by insurance in Korea regardless of whether the patient has breast cancer or not. BRCA testing is also covered by insurance and can be performed in-house; thus, the co-payment is less than 100 USD [21].

In this study, only one patient who underwent RRSO was within the recommended age range according to the current guidelines and most patients were older. The same trend was observed in a previous report that analyzed national-scale data for Japan [22]. The reason may be that most people underwent genetic testing after they developed breast cancer. In the future, the average age of RRSO may decrease if insurance coverage is extended to asymptomatic HBOCs and they undergo genetic testing. Patient number nine was younger but had a 58-mm bifid tumor on her left ovary and she had two children; thus, she strongly desired to remove the tumor.

Hysterectomy at the time of RRSO was performed in all cases with the BRCA1 pathological variant, except for the post-hysterectomy case. We speculate that the reason for this is that information was provided to patients before performing the RRSO. A previous analysis of 1083 women who underwent RRSO without hysterectomy revealed that although the overall risk for uterine cancer after RRSO was not increased, the risk for serous/serous-like endometrial carcinoma was increased in BRCA1 pathogenic women [23]. According to a report by the Japan Society of Obstetrics and Gynecology, the overall 5-year survival rate is good for G1 and G2 endometrioid carcinomas (96.7% and 88.3%, respectively), whereas it is poor for serous endometrial carcinoma (60.9%) [24]. In the case with BRCA1 pathogenic variant, the patient desired a hysterectomy. The composition of hormone replacement therapy was not an argument for hysterectomy in this study. RRSO was covered by insurance, but if there was no abnormality in the uterus, hysterectomy was self-pay, and its cost was approximately 460,000 JPY (3,239 USD). It is important to explain the advantages and disadvantages of hysterectomy before surgery.

This study had three limitations. First, the number of cases was limited because the study was conducted at a single institution. Our institution is the only cancer center in Kanagawa Prefecture, which is the second most populous region in Japan [25]. As other factors were stable in the study period, the results of our institution may reflect the influence of the insurance coverage. Second, the period of time after insurance coverage was relatively short compared with the pre-coverage period. However, the number and acceptance rate of RRSO and BRCA testing increased after insurance coverage; thus, we evaluated the influence of insurance coverage at this point. Third, insurance coverage may have had a potential influence on the counseling of the clinical geneticist; however, this was not evaluated in the present study.