Germline Pathogenic Variants Identified in Patients With Genitourinary Malignancies Undergoing Universal Testing: A Multisite Single-Institution Prospective Study.

PURPOSE: This study aimed to investigate the prevalence of pathogenic germline variants (PGVs) in hereditary cancer genes utilizing a universal testing approach and to determine the rate of PGVs that would have been missed based on National Comprehensive Cancer Network (NCCN) guidelines in genitourinary (GU) malignancies. MATERIALS AND METHODS: A multisite, single-institution prospective germline genetic test (GGT) was universally offered to patients with new or active diagnoses of GU malignancies (prostate, bladder, and renal) from April 2018 to March 2020 at Mayo Clinic sites. Participants were offered GGT using a next-generation sequencing panel of > 80 genes. Demographic, tumor characteristics, and genetic results were evaluated. NCCN GU cancer guidelines were used to identify whether patients had incremental findings, defined as PGV-positive patients who would not have received testing based on NCCN guidelines. RESULTS: Of 3095 individuals enrolled in the study, 601 patients had GU cancer (prostate = 358, bladder = 106, and renal = 137). The mean enrollment age was 67 years (SD 9.1), 89% were male, and 86% of patients were non-Hispanic White. PGVs were identified in 82 (14%) of all GU patients. PGV prevalence breakdown by cancer type was: 14% prostate, 14% bladder, and 13% renal cancer. Nearly one-third of identified PGVs were high penetrance, and the majority of these (67%) were clinically actionable. Incremental PGVs were identified in 28 (57%) prostate, 15 (100%) bladder, and 14 (78%) renal cancer patients. Of the 82 patients with PGV findings, 29 (35%) had at least 1 relative undergo cascade testing for the familial variant(s) identified. CONCLUSIONS: More than 1 in 8 patients with GU malignancies were found to carry a PGV, with 67% of patients with high-penetrance PGVs undergoing clinically actionable changes. The majority of these PGVs would not have been identified based on current testing criteria. These findings support universal GGT for GU malignancies and underscore its potential to enhance risk assessment and guide precision interventions in urologic oncology.

Clinician-Reported Management Recommendations in Response to Universal Germline Genetic Testing in Patients With Prostate Cancer.

PURPOSE: Identification of pathogenic germline variants in patients with prostate cancer can help inform treatment selection, screening for secondary malignancies, and cascade testing. Limited real-world data are available on clinician recommendations following germline genetic testing in patients with prostate cancer. MATERIALS AND METHODS: Patient data and clinician recommendations were collected from unselected patients with prostate cancer who underwent germline testing through the PROCLAIM trial. Differences among groups of patients were determined by 2-tailed Fisher's exact test with significance set at P < .05. Logistic regression was performed to assess the influence of test results in clinical decision-making while controlling for time of diagnosis (newly vs previously diagnosed). RESULTS: Among 982 patients, 100 (10%) were positive (>1 pathogenic germline variant), 482 (49%) had uncertain results (>1 variant of uncertain significance), and 400 (41%) were negative. Patients with positive results were significantly more likely than those with negative or uncertain results to receive recommendations for treatment changes (18% vs 1.4%, P < .001), follow-up changes (64% vs 11%, P < .001), and cascade testing (71% vs 5.4%, P < .001). Logistic regression demonstrated that positive and uncertain results were significantly associated with both changes to treatment and follow-up (P < .001) when controlling for new or previous diagnosis. CONCLUSIONS: Germline genetic testing results informed clinical recommendations for patients with prostate cancer, especially in patients with positive results. Higher than anticipated rates of clinical management changes in patients with uncertain results highlight the need for increased genetic education of clinicians treating patients with prostate cancer.

Universal Germline-Genetic Testing for Breast Cancer: Implementation in a Rural Practice and Impact on Shared Decision-Making.

BACKGROUND: Whereas the National Comprehensive Cancer Network (NCCN) criteria restrict germline-genetic testing (GGT) to a subset of breast cancer (BC) patients, the American Society of Breast Surgeons recommends universal GGT. Although the yield of pathogenic germline variants (PGV) in unselected BC patients has been studied, the practicality and utility of incorporating universal GGT into routine cancer care in community and rural settings is understudied. This study reports real-world implementation of universal GGT for patients with breast cancer and genetics-informed, treatment decision-making in a rural, community practice with limited resources. METHODS: From 2019 to 2022, all patients with breast cancer at a small, rural hospital were offered GGT, using a genetics-extender model. Statistical analyses included Fisher's exact test, t-tests, and calculation of odds ratios. Significance was set at p < 0.05. RESULTS: Of 210 patients with breast cancer who were offered GGT, 192 (91.4%) underwent testing with 104 (54.2%) in-criteria (IC) and 88 (45.8%) out-of-criteria (OOC) with NCCN guidelines. Pathogenic germline variants were identified in 25 patients (13.0%), with PGV frequencies of 15 of 104 (14.4%) in IC and ten of 88 (11.4%) in OOC patients (p = 0.495). GGT informed treatment for 129 of 185 (69.7%) patients. CONCLUSIONS: Universal GGT was successfully implemented in a rural, community practice with > 90% uptake. Treatment was enhanced or de-escalated in those with and without clinically actionable PGVs, respectively. Universal GGT for patients with breast cancer is feasible within rural populations, enabling optimization of clinical care to patients' genetic profile, and may reduce unnecessary healthcare, resource utilization.

Germline cancer susceptibility in individuals with melanoma.

BACKGROUND: Prior studies have estimated a small number of individuals with melanoma (2%-2.5%) have germline cancer predisposition, yet a recent twin study suggested melanoma has the highest hereditability among cancers. OBJECTIVE: To determine the incidence of hereditary melanoma and characterize the spectrum of cancer predisposition genes that may increase the risk of melanoma. METHODS: Four hundred individuals with melanoma and personal or family history of cancers underwent germline testing of >80 cancer predisposition genes. Comparative analysis of germline data was performed on 3 additional oncologic and dermatologic data sets. RESULTS: Germline pathogenic/likely pathogenic (P/LP) variants were identified in 15.3% (61) individuals with melanoma. Most variants (41, 67%) involved genes considered unrelated to melanoma (BLM, BRIP1, CHEK2, MLH1, MSH2, PMS2, RAD51C). A third (20, 33%) were in genes previously associated with familial melanoma (BAP1, BRCA2, CDKN2A, MITF, TP53). Nearly half (30, 46.9%) of P/LP variants were in homologous repair deficiency genes. Validation cohorts demonstrated P/LP rates of 10.6% from an unselected oncologic cohort, 15.8% from a selected commercial testing cohort, and 14.5% from a highly selected dermatologic study. LIMITATIONS: Cohorts with varying degrees of selection, some retrospective. CONCLUSION: Germline predisposition in individuals with melanoma is common, with clinically actionable findings diagnosed in 10.6% to 15.8%.

Racial disparities in cascade testing for cancer predisposition genes.

We sought to determine whether there are racial disparities in cascade testing rates and whether providing testing at no-charge impacts rates in Black and White at-risk-relatives (ARR). Probands with a pathogenic/likely pathogenic germline variant in a cancer predisposition gene were identified up to one year before and up to one year after cascade testing became no-charge in 2017. Cascade testing rates were measured as the proportion of probands who had at least one ARR obtain genetic testing through one commercial laboratory. Rates were compared between self-reported Black and White probands using logistic regression. Interaction between race and cost (pre/post policy) was tested. Significantly fewer Black probands than White probands had at least one ARR undergo cascade genetic testing (11.9% versus 21.7%, OR 0.49, 95% CI 0.39-0.61, p < 0.0001). This was seen both before (OR 0.38, 95% CI 0.24-0.61, p < 0.001) and after (OR 0.53, 95% CI 0.41-0.68, p < 0.001) the no-charge testing policy. Rates of an ARR undergoing cascade testing were low overall, and significantly lower in Black versus White probands. The magnitude of difference in cascade testing rates between Blacks and Whites did not significantly change with no-charge testing. Barriers to cascade testing in all populations should be explored in order to maximize the benefits of genetic testing for both treatment and prevention of cancer.

Fumarate hydratase variant prevalence and manifestations among individuals receiving germline testing.

BACKGROUND: Germline variants in fumarate hydratase (FH) are associated with autosomal dominant (AD) hereditary leiomyomatosis and renal cell cancer (HLRCC) and autosomal recessive (AR) fumarase deficiency (FMRD). The prevalence and cancer penetrance across different FH variants remain unclear. METHODS: A database containing 120,061 records from individuals undergoing cancer germline testing was obtained. FH variants were classified into 3 categories: AD HLRCC variants, AR FMRD variants, and variants of unknown significance (VUSs). Individuals with variants from these categories were compared with those with negative genetic testing. RESULTS: FH variants were detected in 1.3% of individuals (AD HLRCC, 0.3%; AR FMRD, 0.4%; VUS, 0.6%). The rate of AD HLRCC variants discovered among reportedly asymptomatic individuals without a clear indication for HLRCC testing was 1 in 2668 (0.04%). In comparison with those with negative genetic testing, the renal cell carcinoma (RCC) prevalence was elevated with AD HLRCC variants (17.0% vs 4.5%; P < .01) and VUSs (6.4% vs 4.5%; P = .02) but not with AR FMRD variants. CONCLUSIONS: The prevalence of HLRCC discovered incidentally on germline testing is similar to recent population carrier estimates, and this suggests that this is a relatively common cancer syndrome. Compared with those with negative genetic testing, those with VUSs had an elevated risk of RCC, whereas those with AR FMRD variants did not.

CDH1 germline variants are enriched in patients with colorectal cancer, gastric cancer, and breast cancer.

BACKGROUND AND AIMS: CDH1 germline variants have been linked to heritability in diffuse gastric (DGC) and lobular breast cancer (LBC). Studies have not yet assessed whether CDH1 is a cancer-susceptibility gene in other cancers. Herein, we mapped the landscape of pathogenic and likely pathogenic (P/LP) germline variants in CDH1 across various cancers and ethnicities. METHODS: We evaluated CDH1 germline P/LP variants in 212,944 patients at one CLIA-certified laboratory (Invitae) and described their frequency in 7 cancer types. We screened for CDH1 variant enrichment in each cancer relative to a cancer-free population from The Genome Aggregation Database version 3 (gnomADv3). RESULTS: CDH1 P/LP variants were identified in 141 patients, most commonly in patients with DGC (27/408, 6.6%) followed by colorectal signet-ring cell cancer (CSRCC; 3/79, 3.8%), gastric cancer (56/2756, 2%), and LBC (22/6809, 0.3%). CDH1 P/LP variants were enriched in specific ethnic populations with breast cancer, gastric cancer, CRC, LBC, DGC, and CSRCC compared to matched ethnicities from gnomADv3. CONCLUSION: We report for the first time the prevalence of P/LP CDH1 variants across several cancers and show significant enrichment in CDH1 P/LP variants for patients with CSRCC, DGC, and LBC across various ethnicities. Future prospective studies are warranted to validate these findings.

Cancer risks associated with heterozygous ATM loss of function and missense pathogenic variants based on multigene panel analysis.

PURPOSE: Cancer risks conferred by germline, heterozygous, ATM pathogenic/likely pathogenic variants (PSVs) are yet to be consistently determined. The current study assessed these risks by analysis of a large dataset of ATM heterozygote loss of function (LOF) and missense PSV carriers tested with a multigene panel (MGP). METHODS: De-identified data of all individuals who underwent ATM sequencing as part of MGP between October 2015 and February 2020 were reviewed. In cancer cases, rates for the six most prevalent variants and for all LOF and missense PSV combined were compared with rates of the same PSV in ethnically matched, healthy population controls. Statistical analysis included Chi-square tests and odds ratios calculations. RESULTS: For female breast cancer cases, LOF )1794/219,269) and missense (301/219,269) ATM PSVs were seen at higher rates compared to gnomAD non-cancer controls (n = 157/56,001 and n = 27/61,208; p < 0.00001, respectively). Notably, the rate of the c.103C > T variant was higher in controls than in breast cancer cases [p = 0.001; OR 0.31 (95% CI 0.1-0.6)]. For all cancer cases combined, compared with non-cancer population controls, LOF (n = 143) and missense (n = 15) PSVs reported in both datasets were significantly more prevalent in cancer cases [ORLOF 1.7 (95% 1.5-1.9) ORmissense 3.0 (95% CI 2.3-4); p = 0.0001]. CONCLUSION: Both LOF and missense heterozygous ATM PSVs are more frequently detected in cases of several cancer types (breast, ovarian, prostate, lung, pancreatic) compared with healthy population controls. However, not all ATM PSVs confer an increased cancer risk (e.g., breast).

Unexpected actionable genetic variants revealed by multigene panel testing of patients with uterine cancer.

OBJECTIVE: Hereditary uterine cancer (UC) is traditionally associated with pathogenic/likely pathogenic germline variants (PGVs) in Lynch syndrome genes or PTEN; however, growing evidence supports a role for other genes that may reveal new clinical management options. In this study we assessed the prevalence and potential clinical impact of PGVs identified in UC patients referred for comprehensive germline genetic testing that combined testing for Lynch syndrome, PTEN, and other cancer predisposition genes. METHODS: Prevalence of PGVs in patients referred to a single clinical lab for germline genetic testing with an indication of uterine or endometrial cancer were retrospectively assessed and compared by syndrome type, patient age at testing, and self-reported ancestry. Potential clinical actionability of PGVs was based on established guidelines for clinical management, targeted therapies, and clinical trial eligibility. RESULTS: PGVs were detected in 13.6% of the cohort (880/6490). PGVs were most frequently observed in Lynch syndrome genes (60.4%) and PTEN (1.5%), with 38.1% in another cancer predisposition gene (i.e., CHEK2, BRCA1/BRCA2). PGV prevalence was similar for patients <50 years and those ≥50 years (15.1% vs 13.2%). Nearly all PGVs (97.2%) were associated with guideline-recommended management, including cascade testing; 60.5% were associated with FDA-approved therapies; and 35.2% were associated with clinical trials. CONCLUSIONS: Focusing germline testing on Lynch syndrome genes and PTEN and limiting testing to patients <50 years of age at diagnosis may overlook a substantial proportion of UC patients who harbor actionable PGVs. Universal comprehensive genetic testing of UC patients could benefit many patients and at-risk family members.

Cancer Susceptibility Genetic Testing in a High-Risk Cohort of Urban Ashkenazi Jewish Individuals.

Prior to 2013, genetic testing for Ashkenazi Jewish (AJ) individuals primarily consisted of the three-site BRCA1/BRCA2 AJ panel, full sequencing of BRCA1/2, or the Lynch syndrome mismatch repair genes. Multigene panel testing became more widely available in 2013, but limited data are available regarding the impact of multigene panel testing for AJ individuals. Here, we report the frequency of cancer susceptibility gene mutations in a cohort of 427 AJ individuals seen in the Cancer Risk Clinic at The University of Chicago. We found that 29% of affected and 37% of unaffected individuals carried a pathogenic mutation (32% of overall cohort), primarily known familial mutations in BRCA1/2. A minority of mutations were identified in non-BRCA1/2 genes and consisted mainly of AJ founder mutations in CHEK2, APC, and the mismatch repair genes. A panel of AJ founder mutations would have identified the majority (94%) of mutations in clinically actionable genes in both affected and unaffected patients. Based on recent cost-effectiveness studies, offering all AJ individuals a founder mutation panel may be a cost-effective cancer prevention strategy.

Tumor genome analysis includes germline genome: are we ready for surprises?

We sought to describe the spectrum of potential and confirmed germline genomic events incidentally identified during routine medium-throughput somatic tumor DNA sequencing, and to provide a framework for pre- and post-test consent and counseling for patients and families. Targeted tumor-only next-generation sequencing (NGS) had been used to evaluate for possible druggable genomic events obtained from consecutive new patients with metastatic gastroesophageal, hepatobiliary or colorectal cancer seen at the University of Chicago. A panel of medical oncologists, cancer geneticists and genetic counselors retrospectively grouped these patients (N = 111) based on probability of possessing a potentially inherited mutation in a cancer susceptibility gene, both prior to and after incorporating tumor-only NGS results. High-risk patients (determined from NGS results) were contacted and counseled in person by a genetic counselor (N = 21). When possible and indicated, germline genetic testing was offered. Of 8 evaluable high-risk patients, 7 underwent germline testing. Three (37.5%) had confirmed actionable germline mutations (all in the BRCA2 gene). NGS offers promise, but poses significant challenges for oncologists who are ill prepared to handle incidental findings that have clinical implications for at risk family members. In this relatively small cohort of patients undergoing tumor genomic testing for gastrointestinal malignancies, we incidentally identified 3 BRCA2 mutations carriers. This report underscores the need for oncologists to develop a framework for pre- and post-test communication of risks to patients undergoing routine tumor-only sequencing.

Disparate Rates of Germline Variants in Cancer Predisposition Genes in African American/Black Compared With Non-Hispanic White Individuals Between 2015 and 2022.

PURPOSE: African American/Black (AA/B) individuals are under-represented in genomic databases and thus less likely to receive definitive information from germline genetic testing (GGT) than non-Hispanic White (NHW) individuals. With nearly 500,000 AA/B and NHW individuals having undergone multigene panel testing (MGPT) for hereditary cancer risk at a single commercial laboratory, to our knowledge, we present the largest study to date investigating cancer GGT results in AA/B and NHW individuals. METHODS: MGPT results from a retrospective cohort of AA/B (n = 48,684) and NHW (n = 444,831) patients were evaluated. Frequencies of pathogenic germline variants (PGVs) and variants of uncertain significance (VUS) were compared between AA/B and NHW individuals. Changes in frequency of VUS over time were determined. Pearson's chi-squared test was used to compare categorical variables among groups. All significance tests were two-tailed, and P < .05 was considered statistically significant. RESULTS: Between 2015 and 2022, rates of VUS decreased 2.3-fold in AA/B and 1.8-fold in NHW individuals; however, frequencies of VUS and PGV remained significantly higher (46% v 32%; P < .0001) and lower (9% v 13%; P < .0001) in AA/B compared with NHW individuals. Rates of VUS in ATM, BRCA1, BRCA2, PALB2, and PMS2 were significantly higher in AA/B compared with NHW individuals, whereas rates of PGV in BRCA1, BRCA2, and PALB2 were higher in AA/B compared with NHW individuals (P < .001). CONCLUSION: Despite reductions in VUS frequencies over time, disparities in definitive GGT results persist. Increasing inclusion of AA/B populations in both testing and research will further increase knowledge of genetic variants across these racial groups.

Cascade testing for hereditary cancer: comprehensive multigene panels identify unexpected actionable findings in relatives.

Current guidelines recommend single variant testing in relatives of patients with known pathogenic or likely pathogenic germline variants in cancer predisposition genes. This approach may preclude the use of risk-reducing strategies in family members who have pathogenic or likely pathogenic germline variants in other cancer predisposition genes. Cascade testing using multigene panels was performed in 3696 relatives of 7433 probands. Unexpected pathogenic or likely pathogenic germline variants were identified in 230 (6.2%) relatives, including 144 who were negative for the familial pathogenic or likely pathogenic variant but positive for a pathogenic or likely pathogenic variant in a different gene than the proband and 74 who tested positive for the familial pathogenic or likely pathogenic variant and had an additional pathogenic or likely pathogenic variant in a different gene than the proband. Of the relatives with unexpected pathogenic or likely pathogenic germline variants, 36.3% would have qualified for different or additional cancer screening recommendations. Limiting cascade testing to only the familial pathogenic or likely pathogenic variant would have resulted in missed, actionable findings for a subset of relatives.

Multi-Gene Panel Testing for Hereditary Cancer Predisposition Among Patients Sixty-Five Years and Above Diagnosed With Breast Cancer.

Background: The availability and affordability of germline genetic testing (GGT) has resulted in a broader utilization in daily clinical practice. However, adherence to testing guidelines is low, especially among older patients, where testing is often not offered. Methods: In this study, consecutive, newly diagnosed patients with breast cancer (BC) aged ≥ 65 years and eligible for GGT, as per the National Comprehensive Cancer Network (NCCN) guidelines (version 1, 2021), were invited to participate, from March 2021 to December 2022. Patients were offered a restricted (two- or 20-gene panel), or an expanded 84-gene panel. Results: During the study period, 204 patients were enrolled. The mean (standard deviation (SD)) age at BC diagnosis was 70.5 (5.13) years, ranging 65 - 81 years. All patients were Arab and the majority were Jordanian. The majority (n = 188, 92.2%) had early-stage (stages I and II) disease. One hundred three (50.5%) patients were tested with a restricted two-gene (n = 13) or 20-gene (n = 90) panel, while the remaining 101 (49.5%) patients had an expanded 84-gene panel. Family history of close blood relative(s) with BC was the most common indication for testing (n = 110, 53.9%). Among the entire study cohort, 22 (10.8%) had pathogenic/likely pathogenic germline variants (PGVs) and another 97 (47.5%) had ≥ 1 variants of uncertain significance (VUS). PGV rates were significantly higher with the expanded panel (14.9%) compared to restricted testing (6.8%) (P = 0.032). Similarly, VUS rates were significantly higher with the expanded panel (64.4%) compared to the restricted panel (31.1%) (P < 0.001). The most prevalent genes with PGVs were BRCA1/2 (31.3% of all PGV-positive patients), CHEK2 (23.1%) and ATM (19.2%). Conclusion: GGT should not be overlooked in older BC patients, as this study demonstrates that > 10% of patients have PGVs, largely in potentially actionable genes.

Patterns and Frequency of Pathogenic Germline Variants Among Prostate Cancer Patients Utilizing Multi-Gene Panel Genetic Testing.

Background: Germline genetic testing (GGT) has significant implications in the management of patients with prostate cancer (PCa). Herein, we report on patterns and frequency of pathogenic/likely pathogenic germline variants (P/LPGVs) among newly diagnosed Arab patients with PCa. Methods: Patients meeting the National Comprehensive Cancer Network (NCCN) eligibility criteria for GGT were offered a 19-gene PCa panel or an expanded 84-gene multi-cancer panel. Results: During the study period, 231 patients were enrolled; 107 (46.3%) had metastatic disease at diagnosis. In total, 17 P/LPGVs were detected in 17 patients (7.4%). Among the 113 (48.9%) patients who underwent GGT with the 19-gene panel, eight (7.1%) had P/LPGVs, compared to nine (7.6%) of the 118 (51.1%) who did GGT through the expanded 84-gene panel (P = 0.88). Variant of uncertain significance (VUS) rate was higher (n = 73, 61.9%) among the group who underwent expanded 84-gene panel testing compared to those who underwent the 19-gene PCa panel (n = 35, 30.9%) (P = 0.001). P/LPGVs in DNA damage repair (DDR) genes, most frequently BRCA2, CHEK2 and TP53, were the most common P/LPGVs findings. Conclusion: This study is the first to characterize the germline genetic profile of an Arab population with PCa. All detected P/LPGVs were potentially actionable, with most variants able to be detected with a PCa-specific panel.

Implementation of Universal Pan-Cancer Germline Genetic Testing in an Arab Population: The Jordanian Exploratory Cancer Genetics Study.

PURPOSE: Germline genetic testing (GGT) significantly affects cancer care. While universal testing has been studied in Western societies, less is known about adoption elsewhere. MATERIALS AND METHODS: In this study, 3,319 unselected, pan-cancer Jordanian patients diagnosed between April 2021 and September 2022 received GGT. Pathogenic germline variant (PGV) frequency among patients who were in-criteria (IC) or out-of-criteria (OOC; 2020 National Comprehensive Cancer Network criteria) and changes in clinical management in response to GGT results were evaluated. Statistical analysis was performed using two-tailed Fisher's exact test with significance level P < .05. RESULTS: The cohort was predominantly female (69.9%), with a mean age of 53.7 years at testing, and 53.1% were IC. While patients who were IC were more likely than patients who were OOC to have a PGV (15.8% v 9.6%; P < .0001), 149 (34.8%) patients with PGVs were OOC. Clinical management recommendations in response to GGT, including changes to treatment and/or follow-up, were made for 57.3% (161 of 281) of patients with high- or moderate-risk PGVs, including 26.1% (42 of 161) of patients who were OOC. CONCLUSION: Universal GGT of patients with newly diagnosed cancer was successfully implemented in Jordan and led to identification of actionable PGVs that would have been missed with guidelines-based testing.

Retrospective Cohort Study on the Limitations of Direct-to-Consumer Genetic Screening in Hereditary Breast and Ovarian Cancer.

PURPOSE: Among cancer predisposition genes, most direct-to-consumer (DTC) genetic tests evaluate three Ashkenazi Jewish (AJ) founder mutations in BRCA1/2, which represent a small proportion of pathogenic or likely pathogenic variants (PLPV) in cancer predisposing genes. In this study, we investigate PLPV in BRCA1/2 and other cancer predisposition genes that are missed by testing only AJ founder BRCA1/2 mutations. METHODS: Individuals were referred to genetic testing for personal diagnoses of breast and/or ovarian cancer (clinical cohort) or were self-referred (nonindication-based cohort). There were 348,692 participants in the clinical cohort and 7,636 participants in the nonindication-based cohort. Both cohorts were analyzed for BRCA1/2 AJ founder mutations. Full sequence analysis was done for PLPV in BRCA1/2, CDH1, PALB2, PTEN, STK11, TP53, ATM, BARD1, BRIP1, CHEK2 (truncating variants), EPCAM, MLH1, MSH2/6, NF1, PMS2, RAD51C/D, and 22 other genes. RESULTS: BRCA1/2 AJ founder mutations accounted for 10.8% and 29.7% of BRCA1/2 PLPV in the clinical and nonindication-based cohorts, respectively. AJ founder mutations accounted for 89.9% of BRCA1/2 PLPV in those of full AJ descent, but only 69.6% of those of partial AJ descent. In total, 0.5% of all individuals had a BRCA1/2 AJ founder variant, while 7.7% had PLPV in a high-risk breast/ovarian cancer gene. For non-AJ individuals, limiting evaluation to the AJ founder BRCA1/2 mutations missed >90% of mutations in actionable cancer risk genes. Secondary analysis revealed a false-positive rate of 69% for PLPV outside of non-AJ BRCA 1/2 founder mutations. CONCLUSION: DTC genetic testing misses >90% of BRCA1/2 PLPV in individuals of non-AJ ancestry and about 10% of BRCA1/2 PLPV among AJ individuals. There is a high false-positivity rate for non-AJ BRCA 1/2 PLPV with DTC genetic testing.