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.

The AGITG GAP Study: A Phase II Study of Perioperative Gemcitabine and Nab-Paclitaxel for Resectable Pancreas Cancer.

BACKGROUND: While combination therapy with nab-paclitaxel/gemcitabine (nab-gem) is effective in pancreatic ductal adenocarcinoma (PDAC), its efficacy as perioperative chemotherapy is unknown. The primary objective of this multicenter, prospective, single-arm, phase II study was to determine whether neoadjuvant therapy with nab-gem was associated with higher complete resection rates (R0) in resectable PDAC, while the secondary objectives were to determine the utility of radiological assessment of response to preoperative chemotherapy and the safety and efficacy of nab-gem as perioperative therapy. METHODS: Patients were recruited from eight Australian sites, and 42 patients with radiologically defined resectable PDAC and an Eastern Cooperative Oncology Group performance status of 0-2 were enrolled. Participants received two cycles of preoperative nab-paclitaxel 125 mg/m2 and gemcitabine 1000 mg/m2 on days 1, 8, and 15 (28-day cycle) presurgery, and four cycles postoperatively. Early response to chemotherapy was measured with fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scans on day 15. RESULTS: Preoperative nab-gem was completed by 93% of participants, but only 63% postoperatively. Thirty-six patients had surgery: 6 (17%) were unresectable, 15 (52%) had R0 (≥ 1 mm) resections, 14 (48%) had R1 (< 1 mm) resections, and 1 patient did not have PDAC. Median progression-free survival was 12.3 months and median overall survival (OS) was 23.5 months: R0 patients had an OS of 35 months versus 25.6 months for R1 patients after surgery. Seven patients had not progressed after 43 months. CONCLUSIONS: The GAP trial demonstrated that perioperative nab-gem was tolerable. Although the primary endpoint of an 85% R0 rate was not met, the R0 rate was similar to trials using a > 1 mm R0 resection definition, and survival rates were comparable with recent adjuvant studies.

Impact of 2-deoxy-2[F-18]fluoro-D-glucose Positron Emission Tomography on the management of patients with advanced melanoma.

OBJECTIVES: Accurate staging of patients with melanoma is vital to guide appropriate treatment. 2-Deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET) has been reported to be a sensitive and specific technique for the staging of advanced melanoma, however, few studies provide information regarding its impact on patient management. METHODS: We retrospectively reviewed the FDG-PET scan results of 92 patients with melanoma who had 126 scans performed over a six-year period. These patients were seen at the specialist melanoma clinic at our Institution, and 84 patients (92%) had stage III or IV disease. FDG-PET scan results were correlated with computed tomography (CT) scans and other imaging when available, and with clinical follow-up of a minimum of three to six months. The impact of FDG-PET scans on patient management was also assessed. RESULTS: On a lesion-by-lesion analysis, FDG-PET had a sensitivity of 92%, a specificity of 88%, and an accuracy of 91%. FDG-PET correctly affected the clinical decision-making process in 40 of 126 patient studies (32%), particularly assisting in the selection of patients for surgery. CONCLUSION: FDG-PET has an important role in guiding the management of patients with advanced melanoma, particularly when surgery is contemplated.