Pathogenic CDH1 Variants Research Articles

S5154 Management Considerations in a Patient With a CDH1 Pathogenic Variant With a History of Roux-en-Y Gastric Bypass Surgery

S5154 Management Considerations in a Patient With a CDH1 Pathogenic Variant With a History of Roux-en-Y Gastric Bypass Surgery

S424 Multi-Center, International Study of Colonoscopy Findings in Patients With CDH1 and CTNNA1 Germline Pathogenic Variants

S424 Multi-Center, International Study of Colonoscopy Findings in Patients With CDH1 and CTNNA1 Germline Pathogenic Variants

Endoscopic screening for identification of signet ring cell gastric cancer foci in carriers of germline pathogenic variants in CDH1

To determine the preoperative detection of signet ring cancer cells (SRC) on upper endoscopy (EGD) in patients with CDH1 pathogenic variant (PV) undergoing gastrectomy. To evaluate the development of advanced diffuse gastric cancer (DGC) in patients choosing surveillance. Guidelines recommend prophylactic total gastrectomy (pTG) in CDH1 PV carriers with family history of DGC between 18 and 40 years. Annual EGD with biopsies according to established protocols is recommended in carriers with no SRC and no family history of DGC, with consideration of pTG. Retrospective analysis of asymptomatic patients with CDH1 PVs with ≥ 1 surveillance EGD. Outcomes included pre-operative EGD detection of SRC, surgical stage, and progression to advanced DGC in those electing surveillance with EGD. 48 patients with CDH1 PVs who had ≥ 1 EGD were included. 24/ 48 (50%) underwent gastrectomy, including pTG in 7 patients. SRCC were detected on gastrectomy specimen in 21/24 (87.5%). SRCs were identified by EGD in 17/21 patients who had SRCC on gastrectomy specimens (sensitivity 81%, 17/21). All cancers were stage pT1a. The remaining 17 patients (50% with a family history of gastric cancer) continue in annual EGD surveillance with a median follow-up of 34.6 months. No SRCC or advanced DGC have been diagnosed. No CDH1 PV carriers without SRCC on random biopsies followed in an endoscopic program developed advanced DGC over a median follow up of 3 years. In the short term, EGD surveillance might be a safe alternative to immediate pTG in experienced hands in referral centers.

Germline CDH1 Variants and Lifetime Cancer Risk

Approximately 1% to 3% of gastric cancers and 5% of lobular breast cancers are hereditary. Loss of function CDH1 gene variants are the most common gene variants associated with hereditary diffuse gastric cancer and lobular breast cancer. Previously, the lifetime risk of gastric cancer was estimated to be approximately 25% to 83% and for breast cancer it was estimated to be approximately 39% to 55% in individuals with loss of function CDH1 gene variants. To describe gastric and breast cancer risk estimates for individuals with CDH1 variants. Multicenter, retrospective cohort and modeling study of 213 families from North America with a CDH1 pathogenic or likely pathogenic (P/LP) variant in 1 or more family members conducted between January 2021 and August 2022. Hazard ratios (HRs), defined as risk in variant carriers relative to noncarriers, were estimated for each cancer type and used to calculate cumulative risks and risks per decade of life up to age 80 years. A total of 7323 individuals from 213 families were studied, including 883 with a CDH1 P/LP variant (median proband age, 53 years [IQR, 42-62]; 4% Asian; 4% Hispanic; 85% non-Hispanic White; 50% female). In individuals with a CDH1 P/LP variant, the prevalence of gastric cancer was 13.9% (123/883) and the prevalence of breast cancer among female carriers was 26.3% (144/547). The estimated HR for advanced gastric cancer was 33.5 (95% CI, 9.8-112) at age 30 years and 3.5 (95% CI, 0.4-30.3) at age 70 years. The lifetime cumulative risk of advanced gastric cancer in male and female carriers was 10.3% (95% CI, 6%-23.6%) and 6.5% (95% CI, 3.8%-15.1%), respectively. Gastric cancer risk estimates based on family history indicated that a carrier with 3 affected first-degree relatives had a penetrance of approximately 38% (95% CI, 25%-64%). The HR for breast cancer among female carriers was 5.7 (95% CI, 2.5-13.2) at age 30 years and 3.9 (95% CI, 1.1-13.7) at age 70 years. The lifetime cumulative risk of breast cancer among female carriers was 36.8% (95% CI, 25.7%-62.9%). Among families from North America with germline CDH1 P/LP variants, the cumulative risk of gastric cancer was 7% to 10%, which was lower than previously described, and the cumulative risk of breast cancer among female carriers was 37%, which was similar to prior estimates. These findings inform current management of individuals with germline CDH1 variants.

Accurate parent-of-origin variant assignment for multiple hereditary cancer syndromes using proband-only blood sample analysis.

10516 Background: Predicting which side of the family a germline variant comes from is a critical gap in current clinical practice, vital for risk management, variant curation, and cascade genetic testing. Assignment of any autosomal variant to either parent with 99% accuracy is now possible with only a blood sample from the proband. Parent-of-Origin-Aware genomic analysis (POAga) is achieved by combining methylation and sequence data from Oxford Nanopore long-read sequencing with chromosome-length haplotypes generated from Strand-seq to infer parent of origin of any variant along the length of a chromosome, due to accurate phasing of imprinted differentially methylated regions that occur on each autosome. We sought to validate POAga in common, high penetrant hereditary cancer conditions such as hereditary breast and ovarian cancer (HBOC) and Lynch syndrome, rarer syndromes with parent-of-origin-effects and other genes predisposing to breast cancer and gastrointestinal malignancies that are associated with genes across multiple chromosomes. Methods: Blood samples from carriers of pathogenic variants in ATM, BRCA1, BRCA2, CDH1, MLH1, MSH2, MSH6, PMS2, EPCAM, PALB2, SDHD and SDHAF2, with known parental segregation, are currently being ascertained to determine the analytic validity of POAga in real world samples of differing age, sex, ethnicity, and cancer status. Samples are undergoing whole genome analysis by long and short read sequencing. Parent-of-origin of the pathogenic or likely pathogenic variant or variant of uncertain significance is predicted according to previously described methods (Akbari V, Hanlon VCT, et al. Cell Genom. 2022 Dec 21;3(1):100233.) under an REB approved protocol. Results: To date, analysis is complete for 100 individuals with a total of 107 rare or pathogenic germline variants with known or presumed parental segregation. Germline variants are in SDHD (n = 18), BRCA2 (n = 17), BRCA1 (n = 14), MLH1 (n = 10), PALB2 (n = 9), PMS2 (n = 8), MSH2 (n = 9), MSH6 (n = 7), ATM (n = 5), CDH1 (n = 5), SDHAF2 (n = 1), DICER1 (n = 1), MUTYH (n = 1), RET (n = 1), and EPCAM (n = 1). Of variants able to be assigned a parent-of-origin (n = 104 of 107, 97%), there was complete concordance between the predicted parent-of-origin and known clinical segregation (n = 104, 100%). Conclusions: Results to date support the ability of POAga to accurately infer parent-of-origin of rare or pathogenic variants with known parental segregation using only a blood sample from carriers of diverse hereditary cancer syndromes. Ongoing validation of POAga will continue to test its feasibility in real-world samples and inform its path towards clinically translation. Parent-of-Origin-Aware genomic analysis is a powerful technology that could improve our understanding of hereditary cancer syndromes and transform our ability to conduct genetic cancer risk assessments for patients and families.

Abstract PO2-08-11: The MAGIC study: Universal whole genome tumour and germline sequencing of newly diagnosed breast cancer identifies a high proportion of ER+ BRCA-like tumours

Abstract Background: Identification of germline mutations in hereditary breast cancer (HBC) genes can have profound benefits in the treatment of breast cancer (BC) and manging risk for patient and the family. In addition, sequencing of the tumours can reveal clinically relevant somatic features, such as homologous recombination deficiency (HRD) and mutational signatures, that can guide treatment which are not discernible by germline sequencing alone. We hypothesised that current standard of care where women diagnosed with BC are not routinely offered tumour sequencing is suboptimal as fails to exploit all therapeutic vulnerabilities which can be exploited in the treatment of BC. The MAGIC study is the first prospective trial in Australia of unselected invasive BCs in general oncology practice combining both germline and tumour sequencing. Methods: The MAGIC study included a total of 651 consecutive consented patients presenting with non-metastatic BC between June 2020 to March 2023. It included invasive BC, high-grade DCIS and pleomorphic LCIS. The sequencing was conducted in two phases; for phase one, 157 cases underwent whole genome sequencing (WGS) on both germline and matched BC DNA while for phase two, 494 cases underwent only germline whole exome sequencing. Germline variants were interrogated for pathogenic variants in BRCA1, BRCA2, PALB2, ATM, CHEK2, BARD1, BRIP1, RAD51B, RAD51C, RAD51D, MLH1, MSH2, MSH6, PMS2, CDH1, PTEN, STK11, TP53 and NTHL1. Tumour homologous recombination (HR) repair deficiency was calculated using HRDetect (Nat Med 2017;23:517). For BCs showing a high HRDetect score ( >0.75) all HBC gene promoter CpG islands were assessed for hypermethylation using the Twist NGS Methylation system. Mutational signatures were calculated from somatic mutations identified from whole genome sequenced BCs using the DeconstructSig package in R (Genome Biol. 2016;17:31) and referenced against the COSMIC v2 signature catalogue. Results: Actionable germline variants in any HBC gene were identified in 7.7% of cases (7.8% of invasive and 6.1% of in situ BC) with 5.2% having an actionable mutation in an HR pathway gene (BRCA1, BRCA2, PALB2 and RAD51C). Most cases with pathogenic variants showed bi-allelic inactivation in the tumour. All BRCA1, BRCA2 and PALB2 tumours showed high HRDetect and/or HRD scores consistent with loss of HR repair function, indicating them to be the underlying hereditary driver of the BC. One BC with a pathogenic PMS2 variant showed retention of the wild-type allele with no evidence of a mismatch repair mutational signature suggesting PMS2 was not the driver of this BC. Of the 157 BC in phase one that underwent WGS and did not have a germline pathogenic HBC gene variant, 16% (18/117 invasive and 3/13 DCIS) had an HRDetect score of >0.7 indicative of a homologous recombination repair defect and therefore biologically a “BRCA-like” tumour. Of these 21 BRCA-like cases, only 3 invasive BCs had clear somatic bi-allelic inactivation of an HBC gene that could explain the high HRDetect score (2 BRCA1 and 1 BRCA2). One of the 21 BRCA-like cases had a germline variant of unknown significance (VUS) in an HBC gene (a BRCA2 missense variant in an ER+ tumour. The tumour showed loss of the wild-type allele). Of the BRCA-like cases, 71% were ER positive which included 3 invasive lobular cancers. Conclusion: Tumour sequencing identified three times as many cases that might be eligible for HR repair defect targeted therapy than germline testing alone (16% versus 5.2%). Unlike a previous study (Ann Oncol., 2019 30:1071-1079), the majority of the BRCA-like BCs were ER+ with no evidence of a VUS in a known HBC gene suggesting these are driven by novel germline or somatic mutations in genes involved in DNA HR repair. Citation Format: Ian Campbell, Lisa Devereux, Kirsten Hogg, Luxi Lal, Michelle Sinclair, Lesley Stafford, Magnus Zethoven, Anita Skandarajah, Paul James, Geoffrey Lindeman, Bruce Mann, Dilanka De Silva. The MAGIC study: Universal whole genome tumour and germline sequencing of newly diagnosed breast cancer identifies a high proportion of ER+ BRCA-like tumours [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-08-11.

CDH1 Genotype Exploration in Women With Hereditary Lobular Breast Cancer Phenotype

Pathogenic or likely pathogenic (P/LP) germline CDH1 variants are associated with risk for diffuse gastric cancer and lobular breast cancer (LBC) in the so-called hereditary diffuse gastric cancer (HDGC) syndrome. However, in some circumstances, LBC can be the first manifestation of this syndrome in the absence of diffuse gastric cancer manifestation. To evaluate the frequency of germline CDH1 variants in women with the hereditary LBC (HLBC) phenotype, somatic CDH1 gene inactivation in germline CDH1 variant carriers' tumor samples, and the association of genetic profiles with clinical-pathological data and survival. This single-center, longitudinal, prospective cohort study was conducted from January 1, 1997, to December 31, 2021, with follow-up until January 31, 2023. Women with LBC seen at the European Institute of Oncology were included. Testing for germline CDH1, BRCA1, and BRCA2 genes was performed. Somatic profiling was assessed for germline CDH1 carriers. Accurate estimates of prevalence of germline CDH1 variants among patients with HLBC and the association of somatic sequence alteration with HLBC syndrome. The Kaplan-Meier method and a multivariable Cox proportional hazards regression model were applied for overall and disease-free survival analysis. Of 5429 cases of primary LBC, familial LBC phenotype accounted for 1867 (34.4%). A total of 394 women with LBC were tested, among whom 15 germline CDH1 variants in 15 unrelated families were identified. Among these variants, 6 (40.0%) were P/LP, with an overall frequency of 1.5% (6 of 394). Of the 6 probands with P/LP CDH1 LBC, 5 (83.3%) had a positive family history of BC and only 1 (16.7%) had sporadic juvenile early-onset LBC. No germline BRCA1 and BRCA2 variants were identified in CDH1 carriers. An inactivating CDH1 mechanism (second hit) was identified in 4 of 6 explored matched tumor samples (66.7%) in P/LP germline carriers. The P/LP CDH1 LBC variant carriers had a significantly lower age at diagnosis compared with the group carrying CDH1 variants of unknown significance or likely benign (42.5 [IQR, 38.3-43.0] vs 51.0 [IQR, 45.0-53.0] years; P = .03). In this cohort study, P/LP germline CDH1 variants were identified in individuals not fulfilling the classic clinical criteria for HDGC screening, suggesting that identification of these variants may provide a novel method to test women with LBC with early age at diagnosis and/or positive family history of BC.

Costs of Cancer Prevention: Physical and Psychosocial Sequelae of Risk-Reducing Total Gastrectomy.

Risk-reducing surgery for cancer prevention in solid tumors is a pressing clinical topic because of the increasing availability of germline genetic testing. We examined the short- and long-term outcomes of risk-reducing total gastrectomy (RRTG) and its lesser-known impacts on health-related quality of life (QOL) in individuals with hereditary diffuse gastric cancer syndrome. Individuals who underwent RRTG as part of a single-institution natural history study of hereditary gastric cancers were examined. Clinicopathologic details, acute and chronic operative morbidity, and health-related QOL were assessed. Validated questionnaires were used to determine QOL scores and psycho-social-spiritual measures of healing. One hundred twenty-six individuals underwent RRTG because of a pathogenic or likely pathogenic germline CDH1 variant between October 2017 and December 2021. Most patients (87.3%; 110/126) had pT1aN0 gastric carcinoma with signet ring cell features on final pathology. Acute (<30 days) postoperative major morbidity was low (5.6%; 7/126) and nearly all patients (98.4%) lost weight after total gastrectomy. At 2 years after gastrectomy, 94% (64/68) of patients exhibited at least one chronic complication (ie, bile reflux, dysphagia, and micronutrient deficiency). Occupation change (23.5%), divorce (3%), and alcohol dependence (1.5%) were life-altering consequences attributed to total gastrectomy by some patients. In patients with a median follow-up of 24 months, QOL scores decreased at 1 month after gastrectomy and returned to baseline by 6-12 months. RRTG is associated with life-changing adverse events that should be discussed when counseling patients with CDH1 variants about gastric cancer prevention. The risks of cancer-prevention surgery should not only be judged in the context of likelihood of death due to disease if left untreated, but also based on the real consequences of organ removal.

Defining features of hereditary lobular breast cancer due to CDH1 with magnetic resonance imaging and tumor characteristics

Women with germline pathogenic variants in CDH1, which encodes E-cadherin protein, are at increased lifetime risk of invasive lobular carcinoma (ILC). The associated tumor characteristics of hereditary lobular breast carcinoma (HLBC) in this high-risk population are not well-known. A single-center prospective cohort study was conducted to determine the imaging and pathologic features of HLBC compared to population-based ILC using Surveillance, Epidemiology, and End Results (SEER) data. One hundred fifty-eight women with CDH1 variants were evaluated, of whom 48 (30%) also had an ILC diagnosis. The median age at CDH1 diagnosis was 45 years [interquartile range, IQR 34–57 years] whereas the median age at diagnosis of CDH1 with concomitant ILC (HLBC) was 53 [IQR 45–62] years. Among women with HLBC, 83% (40/48) were identified with CDH1 mutation after diagnosis of ILC. Among 76 women (48%, 76/158) undergoing surveillance for ILC with breast magnetic resonance imaging (MRI), 29% (22/76) had an abnormal MRI result with available biopsy data for comparison. MRI detected ILC in 7 out of 8 biopsy-confirmed cases, corresponding with high sensitivity (88%), specificity (75%), and negative predictive value (98%); however, false-positive and false-discovery rates were elevated also (25% and 68%, respectively). HLBC was most frequently diagnosed at age 40–49 years (44%, 21/48), significantly younger than the common age of diagnosis of ILC in SEER general population data (most frequent age range 60–69 years, 28%; p < 0.001). HLBC tumors were smaller than SEER-documented ILC tumors (median 1.40 vs. 2.00 cm; p = 0.002) and had a higher incidence of background lobular carcinoma in situ (88% vs. 1%; p < 0.001) as well as progesterone receptor positivity (95% vs. 81%, p = 0.032). These findings suggest that HLBC is often detected via conventional screening methods as an early-stage hormone receptor-positive tumor, thus the clinical benefit of intensive screening with MRI may be limited to a subset of women with germline CDH1 variants.

Frequency of CDH1, CTNNA1 and CTNND1 Germline Variants in Families with Diffuse and Mixed Gastric Cancer.

The most well-characterized hereditary form of gastric cancer is hereditary diffuse gastric cancer (HDGC), an autosomal dominant syndrome characterized by an increased risk of diffuse gastric and lobular breast cancer. HDGC is predominantly caused by germline pathogenic variants in the CDH1 gene, and more rarely in the CTNNA1 gene. Furthermore, the International Gastric Cancer Linkage Consortium (IGCLC) guidelines do not clarify whether or not mixed gastric cancer (with a diffuse component) should be considered in the HDGC genetic testing criteria. We aimed to evaluate the contribution of CTNNA1 and CTNND1 germline variants to HDGC. Additionally, we also intended to compare the frequencies of CDH1 and CTNNA1 (and eventually CTNND1) germline variants between patients with diffuse and mixed gastric carcinomas to evaluate if genetic testing for these genes should or should not be considered in patients with the latter. We analyzed the CDH1 gene in 67 cases affected with early-onset/familial mixed gastric carcinomas and the CTNNA1 and CTNND1 genes in 208 cases with diffuse or mixed gastric cancer who had tested negative for CDH1 pathogenic germline variants. A deleterious CTNNA1 germline variant was found in 0.7% (1/141) of diffuse gastric cancer patients meeting the 2020 IGCLC criteria, as compared to the rate of 2.8% of CDH1 deleterious variants found by us in this setting. No deleterious variants were found in CTNND1, but six variants of uncertain significance were identified in this gene. We did not find any pathogenic CDH1, CTNNA1 or CTNND1 variant in index patients with early-onset/familial mixed gastric cancer, so there is no evidence that supports including this tumor type in the testing criteria for germline variants in these genes. The role of the CTNND1 gene in inherited gastric cancer predisposition is still unclear.

CDH1 incidental findings in patients with personal or family history of breast cancer.

10524 Background: Pathogenic variants in CDH1 ( CDH1+) are associated with hereditary diffuse gastric cancer (HDGC), with an increased risk for DGC (~40-83%) and lobular breast cancer (BC) (~64%) [1]. The National Cancer Center Network recommends the inclusion of CDH1 in multi-gene panel testing (MGPT) for patients with significant history of BC, given its classification as a high-risk BC gene [2]. Management includes prophylactic gastrectomy or consideration of annual endoscopic biopsies and high-risk breast screening, with consideration of prophylactic mastectomy. Several studies have identified CD H1+ patients who do not meet the International Gastric Linkage Consortium’s diagnostic criteria for HDGC [3.4,5,6]. These studies have brought concerns of CDH1 pathogenic variants in patients with low risk phenotypes, given the potential for total gastrectomy to reduce DGC risk. Our study aims to investigate our cohort of patients with a personal and/or family history of BC to determine if there is a significant number of CDH1+ patients with a non-classical presentation of HDGC. Methods: 17,208 families with a history of BC who underwent MGPT were seen in a Clinical Cancer Genetics (CCG) high-risk breast clinic between August 2013 and July 2022. They were identified using a prospectively maintained MD Anderson Cancer Center CCG database. Families were categorized by their history of GC and CDH1 status. Results: Among the families, 10,202 (59%) had a proband with a personal history of BC, with a mean age of onset of 51 years. 49 families (0.28%) were CDH1+. 21 CDH1+ families (43%) had no personal and/or family history of GC. Overall, 0.12% of families within the cohort were CDH1+ and had no family history of GC. A chi-square goodness of fit test was performed comparing observed (O) versus expected frequencies (E) (O/E) of families that were: 1) CDH1+ and had a history of GC (28/28), 2) CDH1+ and no history of GC (21/21), 3) CDH1 – (benign variant or variant of unknown significance (VUS)) and a history of GC (180/164), and 4) CDH1- and no history of GC (16,979/16,995). O was determined by using a general population risk of GC (0.81%) and estimated risk of DGC for CDH1+ individuals (58.2%). The X2 was determined to be 1.576, with a p-value of 0.66483. Conclusions: In comparison to the expected frequency of incidental CDH1+ families identified via MGPT, we found that there was not a significant difference in expected and observed frequencies of families based on CDH1 status and presence of GC. These results likely reflect the incomplete penetrance and variable expressivity of HDGC, in addition to reported cases of occult signet ring cell carcinomas in biopsy samples or surgical pathology that has been reported in low risk presenting families [7]. We seek to validate these results with cohort of patients in which the diffuse gastric cancer pathology is known and to expand the analysis in patients specifically with a personal history of lobular breast cancer.

Combined loss of CDH1 and downstream regulatory sequences drive early-onset diffuse gastric cancer and increase penetrance of hereditary diffuse gastric cancer

BackgroundGermline CDH1 pathogenic or likely pathogenic variants cause hereditary diffuse gastric cancer (HDGC). Once a genetic cause is identified, stomachs’ and breasts’ surveillance and/or prophylactic surgery is offered to asymptomatic CDH1 carriers, which is life-saving. Herein, we characterized an inherited mechanism responsible for extremely early-onset gastric cancer and atypical HDGC high penetrance.MethodsWhole-exome sequencing (WES) re-analysis was performed in an unsolved HDGC family. Accessible chromatin and CDH1 promoter interactors were evaluated in normal stomach by ATAC-seq and 4C-seq, and functional analysis was performed using CRISPR-Cas9, RNA-seq and pathway analysis.ResultsWe identified a germline heterozygous 23 Kb CDH1-TANGO6 deletion in a family with eight diffuse gastric cancers, six before age 30. Atypical HDGC high penetrance and young cancer-onset argued towards a role for the deleted region downstream of CDH1, which we proved to present accessible chromatin, and CDH1 promoter interactors in normal stomach. CRISPR-Cas9 edited cells mimicking the CDH1-TANGO6 deletion display the strongest CDH1 mRNA downregulation, more impacted adhesion-associated, type-I interferon immune-associated and oncogenic signalling pathways, compared to wild-type or CDH1-deleted cells. This finding solved an 18-year family odyssey and engaged carrier family members in a cancer prevention pathway of care.ConclusionIn this work, we demonstrated that regulatory elements lying down-stream of CDH1 are part of a chromatin network that control CDH1 expression and influence cell transcriptome and associated signalling pathways, likely explaining high disease penetrance and very young cancer-onset. This study highlights the importance of incorporating scientific–technological updates and clinical guidelines in routine diagnosis, given their impact in timely genetic diagnosis and disease prevention.Graphical abstract

Hereditary Gastric Cancer: Single-Gene or Multigene Panel Testing? A Mono-Institutional Experience

Gastric cancer (GC) has long been a 'Cinderella' among hereditary cancers. Until recently, single-gene testing (SGT) was the only approach to identify high-risk individuals. With the spread of multigene panel testing (MGPT), a debate arose on the involvement of other genes, particularly those pertaining to homologous recombination (HR) repair. We report our mono-institutional experience in genetic counseling and SGT for 54 GC patients, with the detection of nine pathogenic variants (PVs) (9/54:16.7%). Seven out of fifty (14%) patients who underwent SGT for unknown mutations were carriers of a PV in CDH1 (n = 3), BRCA2 (n = 2), BRCA1 (n = 1), and MSH2 (n = 1), while one patient (2%) carried two variants of unknown significance (VUSs). CDH1 and MSH2 emerged as genes involved in early-onset diffuse and later-onset intestinal GCs, respectively. We additionally conducted MGPT on 37 patients, identifying five PVs (13.5%), including three (3/5:60%) in an HR gene (BRCA2, ATM, RAD51D) and at least one VUS in 13 patients (35.1%). Comparing PV carriers and non-carriers, we observed a statistically significant difference in PVs between patients with and without family history of GC (p-value: 0.045) or Lynch-related tumors (p-value: 0.036). Genetic counseling remains central to GC risk assessment. MGPT appeared advantageous in patients with unspecific phenotypes, although it led to challenging results.

Factors associated with detection of hereditary diffuse gastric cancer on endoscopy in individuals with germline CDH1 mutations

Individuals with germline pathogenic CDH1 variants have a high risk of hereditary diffuse gastric cancer. The sensitivity of EGD in detecting signet ring cell carcinoma (SRCC) in this population is low. We aimed to identify endoscopic findings and biopsy practices associated with detection of SRCC. This retrospective cohort included individuals with a germline pathogenic/likely pathogenic CDH1 variant undergoing at least 1 EGD at Memorial Sloan Kettering Cancer Center between January 1, 2006, and March 25, 2022. The primary outcome was detection of SRCC on EGD. Findings on gastrectomy were also assessed. The study included periods before and after implementation of the Cambridge protocol for endoscopic surveillance, allowing for assessment of a spectrum of biopsy practices. Ninety-eight CDH1 patients underwent at least 1 EGD at our institution. SRCC was detected in 20 (20%) individuals on EGD overall and in 50 (86%) of the 58 patients undergoing gastrectomy. Most SRCC foci were detected in the gastric cardia/fundus (EGD, 50%; gastrectomy, 62%) and body/transition zone (EGD, 60%; gastrectomy, 62%). Biopsy results of gastric pale mucosal areas were associated with detection of SRCC (P< .01). The total number of biopsy samples taken on EGD was associated with increased detection of SRCC (P= .01), with 43% detected when≥40 samples were taken. Targeted biopsy sampling of gastric pale mucosal areas and increasing number of biopsy samples taken on EGD were associated with detection of SRCC. SRCC foci were mostly detected in the proximal stomach, supporting updated endoscopic surveillance guidelines. Further studies are needed to refine endoscopic protocols to improve SRCC detection in this high-risk population.

Cancer surveillance as an alternative to prophylactic total gastrectomy in hereditary diffuse gastric cancer: a prospective cohort study.

Loss of function variants in CDH1 are the most frequent cause of hereditary diffuse gastric cancer. Endoscopy is regarded as insufficient for early detection due to the infiltrative phenotype of diffuse-type cancers. Microscopic foci of invasive signet ring cells are pathognomonic of CDH1 and precede development of diffuse gastric cancer. We aimed to assess the safety and effectiveness of endoscopy for cancer interception in individuals with germline CDH1 variants, particularly in those who declined prophylactic total gastrectomy. In this prospective cohort study, we included asymptomatic patients aged 2 years or older with pathogenic or likely pathogenic germline CDH1 variants who underwent endoscopic screening and surveillance at the National Institutes of Health (Bethesda, MD, USA) as part of a natural history study of hereditary gastric cancers (NCT03030404). Endoscopy was done with non-targeted biopsies and one or more targeted biopsy and assessment of focal lesions. Endoscopy findings, pathological data, personal and family cancer history, and demographics were recorded. Procedural morbidity, gastric cancer detection by endoscopy and gastrectomy, and cancer-specific events were assessed. Screening was defined as the initial endoscopy and all subsequent endoscopies were considered surveillance; follow-up endoscopy was at 6 to 12 months. The primary aim was to determine effectiveness of endoscopic surveillance for detection of gastric signet ring cell carcinoma. Between Jan 25, 2017, and Dec 12, 2021, 270 patients (median age 46·6 years [IQR 36·5-59·8], 173 [64%] female participants, 97 [36%] male participants; 250 [93%] were non-Hispanic White, eight [3%] were multiracial, four [2%] were non-Hispanic Black, three [1%] were Hispanic, two [1%] were Asian, and one [<1%] was American Indian or Alaskan Native) with germline CDH1 variants were screened, in whom 467 endoscopies were done as of data cutoff (April 30, 2022). 213 (79%) of 270 patients had a family history of gastric cancer, and 176 (65%) reported a family history of breast cancer. Median follow-up was 31·1 months (IQR 17·1-42·1). 38 803 total gastric biopsy samples were obtained, of which 1163 (3%) were positive for invasive signet ring cell carcinoma. Signet ring cell carcinoma was detected in 76 (63%) of 120 patients who had two or more surveillance endoscopies, of whom 74 had occult cancer detected; the remaining two individuals developed focal ulcerations each corresponding to pT3N0 stage carcinoma. 98 (36%) of 270 patients proceeded to prophylactic total gastrectomy. Among patients who had a prophylactic total gastrectomy after an endoscopy with biopsy samples negative for cancer (42 [43%] of 98), multifocal stage IA gastric carcinoma was detected in 39 (93%). Two (1%) participants died during follow-up, one due to metastatic lobular breast cancer and the other due to underlying cerebrovascular disease, and no participants were diagnosed with advanced stage (III or IV) cancer during follow-up. In our cohort, endoscopic cancer surveillance was an acceptable alternative to surgery in individuals with CDH1 variants who declined total gastrectomy. The low rate of incident tumours (>T1a) suggests that surveillance might be a rational alternative to surgery in individuals with CDH1 variants. Intramural Research Program, National Institutes of Health.

Assessment of pathogenic variation in gynecologic cancer genes in a national cohort

Population-based estimates of pathogenic variation burden in gynecologic cancer predisposition genes are a prerequisite for the development of effective precision public health strategies. This study aims to reveal the burden of pathogenic variants in a comprehensive set of clinically relevant breast, ovarian, and endometrial cancer genes in a large population-based study. We performed a rigorous manual classification procedure to identify pathogenic variants in a panel of 17 gynecologic cancer predisposition genes in a cohort of 7091 individuals, representing 0.35% of the general population. The population burden of pathogenic variants in hereditary gynecologic cancer-related genes in our study was 2.14%. Pathogenic variants in genes ATM, BRCA1, and CDH1 are significantly enriched and the burden of pathogenic variants in CHEK2 is decreased in our population compared to the control population. We have identified a high burden of pathogenic variants in several gynecologic cancer-related genes in the Slovenian population, most importantly in the BRCA1 gene.

Hereditary diffuse gastric cancer in a Japanese family with CDH1 mutation three case reports

BackgroundGermline pathogenic variants in the E-cadherin gene CDH1 cause hereditary diffuse gastric cancer (HDGC), which is an autosomal dominant cancer syndrome, accounting for 1–3% of all gastric cancers. HDGC harboring a CDH 1 variant is extremely rare in Japan.MethodIn this study we report the clinical courses of three cases with HDGC from a single Japanese family.ResultsThe proband exhibited advanced and metastatic gastric cancer, and was found to have a previously reported heterozygous frameshift variant in CDH1 (NM_004360.3:c.1009_1010del:p.Ser337Phefs*12). Five at-risk relatives underwent presymptomatic molecular testing after careful genetic counseling, and three were molecularly diagnosed as positive for the variant. Esophagogastroduodenoscopy was performed in these relatives revealing abnormal small pale mucosal patches, small ulcerative lesion and no abnormal findings. Moreover, random and targeted biopsies were compatible with pathological diagnosis of HDGC in the three cases, all of which underwent total prophylactic gastrectomy.ConclusionIt is critical for the assessment and management of HDGC patients to be actively offered a multidisciplinary and familial-oriented approach. Notably, genetic screening in suspected individuals and familial members is a determining piece for a higher detection rate and the identification of clinical relevant mutations in both low and high-incidence gastric cancer countries.

Association of CDH1 Germline Variants and Colon Polyp Phenotypes in Patients with Hereditary Diffuse Gastric Cancer.

Germline CDH1 variants resulting in E-cadherin loss of function result in an increased risk of diffuse type gastric cancer and lobular type breast cancer. However, the risk of developing other epithelial neoplasms, specifically colorectal cancer, is unknown. Patients enrolled in a prospective natural history study of hereditary gastric cancer who underwent at least one colonoscopy were evaluated. Out of 300 patients with CDH1 pathogenic or likely pathogenic variants, 85 underwent colonoscopy. More than half of patients (56%, 48/85) had at least one colorectal polyp. Most of those patients (83%, 40/48) had at least one precancerous polyp (adenoma or sessile serrated lesion). More than half (56%) of patients younger than age 45 had a colorectal polyp. Of those with polyps, the most frequent CDH1 variant type was canonical splice site (27%, 13/48) followed by nonsense (21%, 10/48). There was no association between CDH1 variant type and increased likelihood of colorectal polyps. In summary, a majority of CDH1 variant carriers who underwent colonoscopy had colorectal polyps detected, and most subjects were less than 45 years old. This study of colorectal cancer risk based on the prevalence of colorectal polyps in the CDH1 population requires further investigation to appropriately counsel patients on colorectal cancer screening. Clinical trial registry website: https://clinicaltrials.gov/. Clinical trial number: NCT03030404.

Endoscopic surveillance with systematic random biopsy for the early diagnosis of hereditary diffuse gastric cancer: a prospective 16-year longitudinal cohort study

Hereditary diffuse gastric cancer, generally caused by germline pathogenic variants in CDH1, presents with early-onset signet ring cell carcinoma. Prophylactic total gastrectomy is the definitive treatment. Endoscopic surveillance can inform the timing of prophylactic total gastrectomy through detection of microscopic signet ring cell carcinoma foci. However, evidence is scarce about the optimal endoscopic sampling technique and characterisation of signet ring cell carcinoma foci in hereditary diffuse gastric cancer. We aimed to formally assess the diagnostic yield of different sampling strategies and to identify criteria for the characterisation of endoscopic lesions. For this prospective longitudinal cohort study, we included individuals aged 18 years or older at the Cambridge University Hospitals National Health Service (NHS) Foundation Trust who fulfilled testing criteria for hereditary diffuse gastric cancer between June 1, 2005, and July 31, 2021. The primary outcome was detection of intramucosal signet ring cell carcinoma foci. We assessed the detection rate and anatomical location of signet ring cell carcinoma in random biopsy samples taken according to a systematic protocol compared with biopsies targeted to endoscopic findings. Endoscopic lesions were examined with white-light and narrow band imaging with magnification to assess the likelihood of cancerous foci. 145 individuals were included, of whom 68 (47%) were male and 92 (63%) carried the CDH1 pathogenic variant. 58 (40%) patients were diagnosed with invasive signet ring cell carcinoma over a median follow-up time of 51 months (IQR 18-80). The first diagnosis of signet ring cell carcinoma was most commonly made from random biopsies (29 [50%] of 58 patients), rather than targeted biopsies (15 [26%] patients). The anatomical distribution of signet ring cell carcinoma foci detected by random biopsies more accurately reflected those identified in prophylactic total gastrectomy specimens than did targeted biopsies. Omitting random biopsies in our cohort would have led to an under-diagnosis rate of 42%. Using a novel panel of endoscopic criteria, gastric lesions containing signet ring cell carcinoma were predicted with a sensitivity of 67·3% and a specificity of 90·2%. Random biopsies enhance the early detection of signet ring cell carcinoma and are complementary to targeted biopsies in surveillance of hereditary diffuse gastric cancer. This sampling method should be the standard of care when performing all surveillance endoscopies for individuals with hereditary diffuse gastric cancer. UK Medical Research Council.

Optimising clinical care through CDH1-specific germline variant curation: improvement of clinical assertions and updated curation guidelines

BackgroundGermline pathogenic variants in CDH1 are associated with increased risk of diffuse gastric cancer and lobular breast cancer. Risk reduction strategies include consideration of prophylactic surgery, thereby making accurate interpretation...