DNA Mismatch Repair Gene Variant Classification: Evaluating the Utility of Somatic Mutations and Mismatch Repair Deficient Colonic Crypts and Endometrial Glands.

Germline pathogenic variants in the DNA mismatch repair (MMR) genes (Lynch syndrome) predispose to colorectal (CRC) and endometrial (EC) cancer. Lynch syndrome specific tumor features were evaluated for their ability to support the ACMG/InSiGHT framework in classifying variants of uncertain clinical significance (VUS) in the MMR genes. Twenty-eight CRC or EC tumors from 25 VUS carriers (6xMLH1, 9xMSH2, 6xMSH6, 4xPMS2), underwent targeted tumor sequencing for the presence of microsatellite instability/MMR-deficiency (MSI-H/dMMR) status and identification of a somatic MMR mutation (second hit). Immunohistochemical testing for the presence of dMMR crypts/glands in normal tissue was also performed. The ACMG/InSiGHT framework reclassified 7/25 (28%) VUS to likely pathogenic (LP), three (12%) to benign/likely benign, and 15 (60%) VUS remained unchanged. For the seven re-classified LP variants comprising nine tumors, tumor sequencing confirmed MSI-H/dMMR (8/9, 88.9%) and a second hit (7/9, 77.8%). Of these LP reclassified variants where normal tissue was available, the presence of a dMMR crypt/gland was found in 2/4 (50%). Furthermore, a dMMR endometrial gland in a carrier of an MSH2 exon 1-6 duplication provides further support for an upgrade of this VUS to LP. Our study confirmed that identifying these Lynch syndrome features can improve MMR variant classification, enabling optimal clinical care.

The clinical utility and costs of whole-genome sequencing to detect cancer susceptibility variants-a multi-site prospective cohort study.

BACKGROUND: Many families and individuals do not meet criteria for a known hereditary cancer syndrome but display unusual clusters of cancers. These families may carry pathogenic variants in cancer predisposition genes and be at higher risk for developing cancer. METHODS: This multi-centre prospective study recruited 195 cancer-affected participants suspected to have a hereditary cancer syndrome for whom previous clinical targeted genetic testing was either not informative or not available. To identify pathogenic disease-causing variants explaining participant presentation, germline whole-genome sequencing (WGS) and a comprehensive cancer virtual gene panel analysis were undertaken. RESULTS: Pathogenic variants consistent with the presenting cancer(s) were identified in 5.1% (10/195) of participants and pathogenic variants considered secondary findings with potential risk management implications were identified in another 9.7% (19/195) of participants. Health economic analysis estimated the marginal cost per case with an actionable variant was significantly lower for upfront WGS with virtual panel ($8744AUD) compared to standard testing followed by WGS ($24,894AUD). Financial analysis suggests that national adoption of diagnostic WGS testing would require a ninefold increase in government annual expenditure compared to conventional testing. CONCLUSIONS: These findings make a case for replacing conventional testing with WGS to deliver clinically important benefits for cancer patients and families. The uptake of such an approach will depend on the perspectives of different payers on affordability.

A tumor focused approach to resolving the etiology of DNA mismatch repair deficient tumors classified as suspected Lynch syndrome.

Routine screening of tumors for DNA mismatch repair (MMR) deficiency (dMMR) in colorectal (CRC), endometrial (EC) and sebaceous skin (SST) tumors leads to a significant proportion of unresolved cases classified as suspected Lynch syndrome (SLS). SLS cases (n = 135) were recruited from Family Cancer Clinics across Australia and New Zealand. Targeted panel sequencing was performed on tumor (n = 137; 80×CRCs, 33×ECs and 24xSSTs) and matched blood-derived DNA to assess for microsatellite instability status, tumor mutation burden, COSMIC tumor mutational signatures and to identify germline and somatic MMR gene variants. MMR immunohistochemistry (IHC) and MLH1 promoter methylation were repeated. In total, 86.9% of the 137 SLS tumors could be resolved into established subtypes. For 22.6% of these resolved SLS cases, primary MLH1 epimutations (2.2%) as well as previously undetected germline MMR pathogenic variants (1.5%), tumor MLH1 methylation (13.1%) or false positive dMMR IHC (5.8%) results were identified. Double somatic MMR gene mutations were the major cause of dMMR identified across each tumor type (73.9% of resolved cases, 64.2% overall, 70% of CRC, 45.5% of ECs and 70.8% of SSTs). The unresolved SLS tumors (13.1%) comprised tumors with only a single somatic (7.3%) or no somatic (5.8%) MMR gene mutations. A tumor-focused testing approach reclassified 86.9% of SLS into Lynch syndrome, sporadic dMMR or MMR-proficient cases. These findings support the incorporation of tumor sequencing and alternate MLH1 methylation assays into clinical diagnostics to reduce the number of SLS patients and provide more appropriate surveillance and screening recommendations.

A tumor focused approach to resolving the etiology of DNA mismatch repair deficient tumors classified as suspected Lynch syndrome.

Routine screening of tumors for DNA mismatch repair (MMR) deficiency (dMMR) in colorectal (CRC), endometrial (EC) and sebaceous skin (SST) tumors leads to a significant proportion of unresolved cases classified as suspected Lynch syndrome (SLS). SLS cases (n=135) were recruited from Family Cancer Clinics across Australia and New Zealand. Targeted panel sequencing was performed on tumor (n=137; 80xCRCs, 33xECs and 24xSSTs) and matched blood-derived DNA to assess for microsatellite instability status, tumor mutation burden, COSMIC tumor mutational signatures and to identify germline and somatic MMR gene variants. MMR immunohistochemistry (IHC) and MLH1 promoter methylation were repeated. In total, 86.9% of the 137 SLS tumors could be resolved into established subtypes. For 22.6% of these resolved SLS cases, primary MLH1 epimutations (2.2%) as well as previously undetected germline MMR pathogenic variants (1.5%), tumor MLH1 methylation (13.1%) or false positive dMMR IHC (5.8%) results were identified. Double somatic MMR gene mutations were the major cause of dMMR identified across each tumor type (73.9% of resolved cases, 64.2% overall, 70% of CRC, 45.5% of ECs and 70.8% of SSTs). The unresolved SLS tumors (13.1%) comprised tumors with only a single somatic (7.3%) or no somatic (5.8%) MMR gene mutations. A tumor-focused testing approach reclassified 86.9% of SLS into Lynch syndrome, sporadic dMMR or MMR-proficient cases. These findings support the incorporation of tumor sequencing and alternate MLH1 methylation assays into clinical diagnostics to reduce the number of SLS patients and provide more appropriate surveillance and screening recommendations.

Mainstream genetic testing for high-grade ovarian, tubal and peritoneal cancers: A tertiary referral centre experience.

BACKGROUND: Fifteen percent of ovarian, tubal, and peritoneal (OTP) invasive epithelial cancers are linked to an underlying heritable pathogenic variant (PV) in the BRCA1/2 cancer susceptibility genes. Identifying a PV has management implications for an affected individual and relatives. Cancer team-facilitated genetic testing (mainstreaming) aims to provide equitable systematic access to genetic testing for appropriate patients. AIM: To evaluate a multi-disciplinary team (MDT)-led mainstream germline genetic testing program for OTP cancer at a tertiary referral centre. MATERIALS AND METHODS: We conducted a retrospective review of our MDT-led mainstream genetic testing program initiated in June 2017. We included all patients diagnosed with OTP cancer registered with the hospital gynaecological oncology MDT from program initiation to December 2020. Patients were considered eligible for testing if they were diagnosed with a high-grade epithelial OTP AND ≤70 years, OR if >70 with a first/second degree relative with breast and/or ovarian cancer OR Jewish ancestry. RESULTS: Of 205 women diagnosed with high-grade epithelial OTP cancer, 140 were eligible for mainstreaming. Eight-five percent were mainstreamed, with the gynae-oncologists facilitating 64.5% of tests. The overall PV detection rate in BRCA1/2 was 10.1% (BRCA1 n = 9, BRCA2 n = 3). The median turnaround time (TAT) was 44.5 days (range 16-118). All women with PV were referred to the Familial Cancer Service for further assessment and five (of six eligible; 83%) were subsequently treated with polyadenosine diphosphate ribose polymerase inhibitors. Cascade testing was undertaken in 75% of families with a mean of three relatives tested per proband. CONCLUSION: Mainstreamed genetic testing is feasible, with an acceptable TAT, ensuring adequate opportunity to inform treatment decisions. Tumour testing and inclusion of moderate-risk cancer predisposition genes in mainstreaming represent potential pathways that will require further exploration.

Lynch syndrome testing of colorectal cancer patients in a high-income country with universal healthcare: a retrospective study of current practice and gaps in seven australian hospitals.

BACKGROUND: To inform effective genomic medicine strategies, it is important to examine current approaches and gaps in well-established applications. Lynch syndrome (LS) causes 3-5% of colorectal cancers (CRCs). While guidelines commonly recommend LS tumour testing of all CRC patients, implementation in health systems is known to be highly variable. To provide insights on the heterogeneity in practice and current bottlenecks in a high-income country with universal healthcare, we characterise the approaches and gaps in LS testing and referral in seven Australian hospitals across three states. METHODS: We obtained surgery, pathology, and genetics services data for 1,624 patients who underwent CRC resections from 01/01/2017 to 31/12/2018 in the included hospitals. RESULTS: Tumour testing approaches differed between hospitals, with 0-19% of patients missing mismatch repair deficiency test results (total 211/1,624 patients). Tumour tests to exclude somatic MLH1 loss were incomplete at five hospitals (42/187 patients). Of 74 patients with tumour tests completed appropriately and indicating high risk of LS, 36 (49%) were missing a record of referral to genetics services for diagnostic testing, with higher missingness for older patients (0% of patients aged ≤ 40 years, 76% of patients aged > 70 years). Of 38 patients with high-risk tumour test results and genetics services referral, diagnostic testing was carried out for 25 (89%) and identified a LS pathogenic/likely pathogenic variant for 11 patients (44% of 25; 0.7% of 1,624 patients). CONCLUSIONS: Given the LS testing and referral gaps, further work is needed to identify strategies for successful integration of LS testing into clinical care, and provide a model for hereditary cancers and broader genomic medicine. Standardised reporting may help clinicians interpret tumour test results and initiate further actions.

Real world outcomes and implementation pathways of exome sequencing in an adult genetic department.

PURPOSE: This study aimed to correlate the indications and diagnostic yield of exome sequencing (ES) in adult patients across various clinical settings. The secondary aim was to examine the clinical utility of ES in adult patients. METHODS: Data on demographics, clinical indications, results, management changes, and cascade testing were collected for 250 consecutive patients who underwent ES through an adult genetics department between 2016 and 2021. Data were analyzed using descriptive and inferential statistics. Testing in which traditional gene panels were in standard use, such as in heritable cancers, was excluded. RESULTS: The average age at testing was 43 years (range = 17-80 years). A molecular diagnosis was identified in 29% of patients. Older age at symptom onset did not pre-exclude a substantial diagnostic yield. Patients with syndromic intellectual disability and multiple system disorders had the highest yield. In >50% of patients with an exome diagnosis, the results changed management. Cascade testing occured in at least one family member for 30% of patients with a diagnosis. Diagnostic results had reproductive implications for 26% of patients and 31% of patients' relatives. CONCLUSION: ES has a robust diagnostic yield and clear clinical utility in adult patients across a range of ages and phenotypes.

Older adults' preferred and perceived roles in decision-making about palliative chemotherapy, decision priorities and information preferences.

AIM: Patients with cancer have varied preferences for involvement in decision-making. We sought older adults' preferred and perceived roles in decision-making about palliative chemotherapy; priorities; and information received and desired. METHODS: Patients ≥65y who had made a decision about palliative chemotherapy with an oncologist completed a written questionnaire. Preferred and perceived decision-making roles were assessed by the Control Preferences Scale. Wilcoxon rank-sum tests evaluated associations with preferred role. Factors important in decision-making were rated and ranked, and receipt of, and desire for information was described. RESULTS: Characteristics of the 179 respondents: median age 74y, male (64%), having chemotherapy (83%), vulnerable (Vulnerable Elders Survey-13 score ≥ 3) (52%). Preferred decision-making roles (n = 173) were active in 39%, collaborative in 27%, and passive in 35%. Perceived decision-making roles (n = 172) were active in 42%, collaborative in 22%, and passive in 36% and matched the preferred role for 63% of patients. Associated with preference for an active role: being single/widowed (p = .004, OR = 1.49), having declined chemotherapy (p = .02, OR = 2.00). Ranked most important (n = 159) were "doing everything possible" (30%), "my doctor's recommendation" (26%), "my quality of life" (20%), and "living longer" (15%). A minority expected chemotherapy to cure their cancer (14%). Most had discussed expectations of cure (70%), side effects (88%) and benefits (82%) of chemotherapy. Fewer had received quantitative prognostic information (49%) than desired this information (67%). CONCLUSION: Older adults exhibited a range of preferences for involvement in decision-making about palliative chemotherapy. Oncologists should seek patients' decision-making preferences, priorities, and information needs when discussing palliative chemotherapy.