Family history and BRCA1/BRCA2 status among Japanese ovarian cancer patients and occult cancer in a BRCA1 mutant case

Using species richness calculations to model the global profile of unsampled pathogenic variants: Examples from BRCA1 and BRCA2

There have been many surveys of genetic variation in BRCA1 and BRCA2 to identify variant prevalence and catalogue population specific variants, yet none have evaluated the magnitude of unobserved variation. We applied species richness estimation methods from ecology to estimate "variant richness" and determine how many germline pathogenic BRCA1/2 variants have yet to be identified and the frequency of these missing variants in different populations. We also estimated the prevalence of germline pathogenic BRCA1/2 variants and identified those expected to be most common. Data was obtained from a literature search including studies conducted globally that tested the entirety of BRCA1/2 for pathogenic variation. Across countries, 45% to 88% of variants were estimated to be missing, i.e., present in the population but not observed in study data. Estimated variant frequencies in each country showed a higher proportion of rare variants compared to recurrent variants. The median prevalence estimate of BRCA1/2 pathogenic variant carriers was 0.64%. BRCA1 c.68_69del is likely the most recurrent BRCA1/2 variant globally due to its estimated prevalence in India. Modeling variant richness using ecology methods may assist in evaluating clinical targeted assays by providing a picture of what is observed with estimates of what is still unknown.

Retrospective evaluation of risk-reducing salpingo-oophorectomy for BRCA1/2 pathogenic variant carriers among a cohort study in a single institution

BACKGROUND

Risk-reducing salpingo-oophorectomy is performed for the primary prevention of ovarian cancer in patients with hereditary breast-ovarian cancer syndrome. We performed risk-reducing salpingo-oophorectomy for the first time in Japan in 2008, and we experienced 20 cases of risk-reducing salpingo-oophorectomy through 2019. In the past, the use of risk-reducing salpingo-oophorectomy in Japan was restricted because it was not covered by a Japanese National Health Insurance. Since April 2020, risk-reducing salpingo-oophorectomy has been covered by insurance for patients with breast-ovarian cancer syndrome and pre-existing breast cancer, and this surgery is expected to become more widely implemented in Japan.

METHODS

To contribute to the widespread use of risk-reducing salpingo-oophorectomy in the future, we retrospectively reviewed 20 cases of risk-reducing salpingo-oophorectomy at our hospital cohort study to clarify the issues in its implementation.

RESULTS

The variant genes for which risk-reducing salpingo-oophorectomy was indicated were BRCA1 and BRCA2 in 13 (65%) and 7 patients (35%), respectively. The median age at which risk-reducing salpingo-oophorectomy was performed was 49 years (range, 38-58), 13 patients (65%) had gone through menopause, and 16 patients (80%) had a history of breast cancer. Of the five patients (25%) with vasomotor symptoms, four received Chinese medicine, and only one received hormone replacement therapy. Occult cancer was detected in the removed ovaries in two patients (10%), although no postoperative peritoneal carcinogenesis has been observed to date.

CONCLUSIONS

Women who paid for risk-reducing salpingo-oophorectomy out of pocket were older than the recommended age at which the procedure should be performed, and this may explain the higher rate of occult cancers than previously reported. We need to perform risk-reducing salpingo-oophorectomy at the recommended age to ensure that the procedure is effective for primary prevention.

Dietary fiber intake is associated with a reduced risk of ovarian cancer: a dose-response meta-analysis

Dietary fiber may reduce the bioavailability of steroid hormones and favorably regulate insulin-like growth factor 1, and therefore may be associated with ovarian cancer risk. Current evidence on the association between dietary fiber intake and risk of ovarian cancer is inconsistent. Therefore, we conducted a meta-analysis to explore the association. We hypothesized that dietary fiber intake might be associated with a reduced risk of ovarian cancer. PubMed, Web of Science, Embase, China National Knowledge Infrastructure, and Wanfang databases were searched for relevant articles up to September 2017. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated using random-effects model. Dose-response relationship was assessed by restricted cubic spline. A total of 19 studies involving 567 742 participants were included in this meta-analysis. The summary RR of the association between dietary fiber intake and ovarian cancer risk was 0.70 (95% CI, 0.57-0.87; I² = 83.5%, P_{heterogeneity} < .001). In subgroup analyses, the above-mentioned significant inverse association was found among studies conducted in North America, case-control studies, and studies assessing the association of total fiber intake with ovarian cancer risk. Dose-response analysis suggested that ovarian cancer risk decreased by 3% (RR, 0.97; 95% CI, 0.95-0.99) for each 5-g/d increment in dietary fiber intake. This meta-analysis suggests that dietary fiber intake is associated with a reduced risk of ovarian cancer. Future intervention trials are needed to test the associations between different types of fiber (including soluble, insoluble, vegetable, fruit, cereal, and legumes fiber) and ovarian cancer risk.

Prevalence and clinical significance of BRCA1/2 germline and somatic mutations in Taiwanese patients with ovarian cancer

Germline and somatic BRCA1/2 mutations define a subset of patients with ovarian cancer who may benefit from treatment with poly (ADP-ribose) polymerase inhibitors. Unfortunately, data on the frequency of BRCA1/2 germline mutations in Taiwanese patients with ovarian cancer are scarce, with the prevalence of somatic mutations being unknown. We aim to investigate the occurrence of BRCA1/2 mutations in 99 Taiwanese patients with ovarian cancer which included serous (n = 46), endometrioid (n = 24), and clear cell (n = 29) carcinomas. BRCA1/2 mutations were identified using next-generation sequencing of formalin-fixed paraffin-embedded tumor samples. Pathogenic variants (BRCA1: n = 7; BRCA2: n = 6) were detected in 12.1% (12/99) of the study patients. Somatic and germline BRCA1/2 mutation rates in serous ovarian cancer are 4/46 (8.7%) and 8/46 (17%), respectively. All of the pathogenic BRCA1/2 mutations were identified in serous carcinoma samples (12/46; 26.1%). One-third (4/12) of the deleterious BRCA1/2 mutations occurred in tumor tissues only (somatic mutations). All of them coexisted with loss of heterozygosity, resulting in biallelic BRCA inactivation. Five novel pathogenic mutations were identified, including four somatic variants (BRCA1 p.S242fs, BRCA1 p.F989fs, BRCA1 p.G1738fs, and BRCA2 p.D1451fs) and a germline variant (BRCA2 p.E260fs). We also detected additional six novel mutations (three in BRCA1 and three in BRCA2) with pathogenic potentials. We conclude that BRCA1/2 mutations are common in Taiwanese patients with serous ovarian carcinoma and similar to mutation rates in other ethnic groups. The analysis of BRCA1/2 somatic mutations is crucial for guiding therapeutic decisions in ovarian cancer.

Prevalence of pathogenic germline variants detected by multigene sequencing in unselected Japanese patients with ovarian cancer

Pathogenic germline BRCA1, BRCA2 (BRCA1/2), and several other gene variants predispose women to primary ovarian, fallopian tube, and peritoneal carcinoma (OC), although variant frequency and relevance information is scarce in Japanese women with OC. Using targeted panel sequencing, we screened 230 unselected Japanese women with OC from our hospital-based cohort for pathogenic germline variants in 75 or 79 OC-associated genes. Pathogenic variants of 11 genes were identified in 41 (17.8%) women: 19 (8.3%; BRCA1), 8 (3.5%; BRCA2), 6 (2.6%; mismatch repair genes), 3 (1.3%; RAD51D), 2 (0.9%; ATM), 1 (0.4%; MRE11A), 1 (FANCC), and 1 (GABRA6). Carriers of BRCA1/2 or any other tested gene pathogenic variants were more likely to be diagnosed younger, have first or second-degree relatives with OC, and have OC classified as high-grade serous carcinoma (HGSC). After adjustment for these variables, all 3 features were independent predictive factors for pathogenic variants in any tested genes whereas only the latter two remained for variants in BRCA1/2. Our data indicate similar variant prevalence in Japanese patients with OC and other ethnic groups and suggest that HGSC and OC family history may facilitate genetic predisposition prediction in Japanese patients with OC and referring high-risk patients for genetic counseling and testing.

TP53 mutations in epithelial ovarian cancer

Genomic sequencing analyses of a variety of human cancers have revealed that massive mutations of cancer-relevant genes are the major alterations in cancerous cells, and their mutation frequencies or rates are highly associated with the development, progression, metastasis, and drug resistance of cancers as well as their clinical outcomes and prognosis. One predominant genetic alternation in human epithelial ovarian cancer (EOC) is the mutation of TP53 that encodes the tumor suppressor p53 protein. This essay will review the most recent progress in understanding the role of TP53 mutations in development, progression, and metastasis of EOC, and discuss the potential of TP53 mutations as diagnostic and prognostic biomarkers as well as therapeutic targets for EOC.

Serous tubal intraepithelial carcinoma in a Japanese woman with a deleterious BRCA1 mutation

Risk-reducing salpingo-oophorectomy for reducing future cancer risk in women with hereditary breast and ovarian cancer syndrome is rarely performed in Japan; therefore, the cancer preventive effect of risk-reducing salpingo-oophorectomy for hereditary breast and ovarian cancer syndrome among the Japanese population remains unclear. Here, we report the first case of serous tubal intraepithelial carcinoma identified through a risk-reducing salpingo-oophorectomy in a Japanese woman with hereditary breast and ovarian cancer syndrome and who had a deleterious germline mutation of E1214X in BRCA1, but not a BRCA2 mutation. A pre-operative examination revealed multiple uterine leiomyomas but no adnexal mass. Robotic-assisted bilateral salpingo-oophorectomy together with hysterectomy was performed. A pathological examination identified serous tubal intraepithelial carcinoma in the right fallopian tube with no dissemination. Serous tubal intraepithelial carcinoma is implicated as an origin of invasive cancer of the fallopian tube with peritoneal dissemination; prophylactic salpingo-oophorectomy is currently the only method to identify this occult cancer. Our case demonstrated that risk-reducing salpingo-oophorectomy can detect occult cancers, including serous tubal intraepithelial carcinoma, thereby preventing future cancer development in the Japanese hereditary breast and ovarian cancer syndrome population.