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      Investigation on the hereditary basis of colorectal cancers in an African population with frequent early onset cases

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          Abstract

          Background

          Approximately 25% of colorectal cancer patients in sub-Saharan Africa are younger than 40 years, and hereditary factors may contribute. We investigated the frequency and patterns of inherited colorectal cancer among black Zimbabweans.

          Methods

          A population-based cross-sectional study of ninety individuals with a new diagnosis of colorectal cancer was carried out in Harare, Zimbabwe between November 2012 and December 2015. Phenotypic data was obtained using interviewer administered questionnaires, and reviewing clinical and pathology data. Cases were screened for mismatch repair deficiency by immunohistochemistry and/or microsatellite instability testing, and for MLH1, MSH2 and EPCAM deletions using multiplex ligation-dependent probe amplification. Next generation sequencing using a 16-gene panel was performed for cases with phenotypic features consistent with familial colorectal cancer. Variants were assessed for pathogenicity using the mean allele frequency, phenotypic features and searching online databases.

          Results

          Three Lynch syndrome cases were identified: MSH2 c. 2634G>A pathogenic mutation, c. (1896+1_1897–1)_(*193_? )del , and one fulfilling the Amsterdam criteria, with MLH1 and PMS2 deficiency, but no identifiable pathogenic mutation. Two other cases had a strong family history of cancers, but the exact syndrome was not identified. The prevalence of Lynch syndrome was 3·3% (95% CI 0·7–9·4), and that of familial colorectal cancer was 5·6% (95% CI, 1·8–12·5).

          Conclusions

          Identifying cases of inherited colorectal cancer in sub-Saharan Africa is feasible, and our findings can inform screening guidelines appropriate to this setting.

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          Most cited references20

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          Feasibility of screening for Lynch syndrome among patients with colorectal cancer.

          Identifying individuals with Lynch syndrome (LS) is highly beneficial. However, it is unclear whether microsatellite instability (MSI) or immunohistochemistry (IHC) should be used as the screening test and whether screening should target all patients with colorectal cancer (CRC) or those in high-risk subgroups. MSI testing and IHC for the four mismatch repair proteins was performed on 500 tumors from unselected patients with CRC. If either MSI or IHC was abnormal, complete mutation analysis for the mismatch repair genes was performed. Among the 500 patients, 18 patients (3.6%) had LS. All 18 patients detected with LS (100%) had MSI-high tumors; 17 (94%) of 18 patients with LS were correctly predicted by IHC. Of the 18 probands, only eight patients (44%) were diagnosed at age younger than 50 years, and only 13 patients (72%) met the revised Bethesda guidelines. When these results were added to data on 1,066 previously studied patients, the entire study cohort (N = 1,566) showed an overall prevalence of 44 of 1,566 patients (2.8%; 95% CI, 2.1% to 3.8%) for LS. For each proband, on average, three additional family members carried MMR mutations. One of every 35 patients with CRC has LS, and each has at least three relatives with LS; all of whom can benefit from increased cancer surveillance. For screening, IHC is almost equally sensitive as MSI, but IHC is more readily available and helps to direct gene testing. Limiting tumor analysis to patients who fulfill Bethesda criteria would fail to identify 28% (or one in four) cases of LS.
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            Cancer Susceptibility Gene Mutations in Individuals With Colorectal Cancer.

            Purpose Hereditary factors play an important role in colorectal cancer (CRC) risk, yet the prevalence of germline cancer susceptibility gene mutations in patients with CRC unselected for high-risk features (eg, early age at diagnosis, personal/family history of cancer or polyps, tumor microsatellite instability [MSI], mismatch repair [MMR] deficiency) is unknown. Patients and Methods We recruited 1,058 participants who received CRC care in a clinic-based setting without preselection for age at diagnosis, personal/family history, or MSI/MMR results. All participants underwent germline testing for mutations in 25 genes associated with inherited cancer risk. Each gene was categorized as high penetrance or moderate penetrance on the basis of published estimates of the lifetime cancer risks conferred by pathogenic germline mutations in that gene. Results One hundred five (9.9%; 95% CI, 8.2% to 11.9%) of 1,058 participants carried one or more pathogenic mutations, including 33 (3.1%) with Lynch syndrome (LS). Twenty-eight (96.6%) of 29 available LS CRCs demonstrated abnormal MSI/MMR results. Seventy-four (7.0%) of 1,058 participants carried non-LS gene mutations, including 23 (2.2%) with mutations in high-penetrance genes (five APC, three biallelic MUTYH, 11 BRCA1/2, two PALB2, one CDKN2A, and one TP53), 15 of whom lacked clinical histories suggestive of their underlying mutation. Thirty-eight (3.6%) participants had moderate-penetrance CRC risk gene mutations (19 monoallelic MUTYH, 17 APC*I1307K, two CHEK2). Neither proband age at CRC diagnosis, family history of CRC, nor personal history of other cancers significantly predicted the presence of pathogenic mutations in non-LS genes. Conclusion Germline cancer susceptibility gene mutations are carried by 9.9% of patients with CRC. MSI/MMR testing reliably identifies LS probands, although 7.0% of patients with CRC carry non-LS mutations, including 1.0% with BRCA1/2 mutations.
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              Guidelines on genetic evaluation and management of Lynch syndrome: a consensus statement by the US Multi-Society Task Force on colorectal cancer.

              The Multi-Society Task Force, in collaboration with invited experts, developed guidelines to assist health care providers with the appropriate provision of genetic testing and management of patients at risk for and affected with Lynch syndrome as follows: Figure 1 provides a colorectal cancer risk assessment tool to screen individuals in the office or endoscopy setting; Figure 2 illustrates a strategy for universal screening for Lynch syndrome by tumor testing of patients diagnosed with colorectal cancer; Figures 3-6 provide algorithms for genetic evaluation of affected and at-risk family members of pedigrees with Lynch syndrome; Table 10 provides guidelines for screening at-risk and affected persons with Lynch syndrome; and Table 12 lists the guidelines for the management of patients with Lynch syndrome. A detailed explanation of Lynch syndrome and the methodology utilized to derive these guidelines, as well as an explanation of, and supporting literature for, these guidelines are provided.
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                Author and article information

                Contributors
                Role: ConceptualizationRole: Data curationRole: Formal analysisRole: Funding acquisitionRole: InvestigationRole: MethodologyRole: Writing – original draftRole: Writing – review & editing
                Role: Formal analysisRole: InvestigationRole: MethodologyRole: Writing – review & editing
                Role: ConceptualizationRole: Data curationRole: Writing – review & editing
                Role: Data curationRole: InvestigationRole: Writing – review & editing
                Role: InvestigationRole: MethodologyRole: ResourcesRole: Writing – review & editing
                Role: Formal analysisRole: Writing – review & editing
                Role: Formal analysisRole: Writing – review & editing
                Role: ConceptualizationRole: Funding acquisitionRole: Writing – review & editing
                Role: ConceptualizationRole: Funding acquisitionRole: InvestigationRole: MethodologyRole: Writing – review & editing
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                24 October 2019
                2019
                : 14
                : 10
                : e0224023
                Affiliations
                [1 ] Department of Medicine, College of Health Sciences, University of Zimbabwe, Harare, Zimbabwe
                [2 ] MRC/UCT Research Unit for Genomic and Precision Medicine, Division of Human Genetics, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
                [3 ] Central Analytical Facility (CAF), DNA Sequencing Unit, Stellenbosch University, Stellenbosch, South Africa
                [4 ] Department of Histopathology, College of Health Sciences, University of Zimbabwe, Harare, Zimbabwe
                [5 ] Division of Anatomical Pathology, Faculty of Health Sciences, University of Cape Town, and National Health Laboratory Service Groote Schuur hospital, Cape Town, South Africa
                [6 ] Department of Community Medicine, College of Health Sciences, University of Zimbabwe, Harare, Zimbabwe
                [7 ] Division of Gastroenterology, Department of Medicine, University of Cape Town, Cape Town, Groote Schuur Hospital, Cape Town, South Africa
                CNR, ITALY
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Author information
                http://orcid.org/0000-0003-4815-5207
                Article
                PONE-D-19-03920
                10.1371/journal.pone.0224023
                6812839
                31647837
                f70a0e1f-264f-48a6-81c4-e12ba4ec531f
                © 2019 Katsidzira et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 9 February 2019
                : 4 October 2019
                Page count
                Figures: 2, Tables: 4, Pages: 13
                Funding
                Funded by: funder-id http://dx.doi.org/10.13039/100004440, Wellcome Trust;
                Award ID: WT087537MA
                Funded by: Gastro Foundation of sub-Saharan Africa
                Award Recipient :
                Funded by: Medical Research Council of South Africa
                Award Recipient :
                This work was supported by the Wellcome Trust (Southern African Consortium for Research Excellence initiative, WT087537MA) to LK; the Gastro Foundation of Sub-Saharan Africa to LK and the Medical Research Council of South Africa to RR. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Medicine and Health Sciences
                Oncology
                Cancers and Neoplasms
                Colorectal Cancer
                Medicine and Health Sciences
                Clinical Genetics
                Genetic Diseases
                Autosomal Dominant Diseases
                Hereditary Nonpolyposis Colorectal Cancer
                Biology and life sciences
                Genetics
                DNA
                DNA repair
                Mismatch Repair
                Biology and life sciences
                Biochemistry
                Nucleic acids
                DNA
                DNA repair
                Mismatch Repair
                People and Places
                Geographical Locations
                Africa
                Biology and life sciences
                Molecular biology
                Molecular biology techniques
                Sequencing techniques
                DNA sequencing
                Next-Generation Sequencing
                Research and analysis methods
                Molecular biology techniques
                Sequencing techniques
                DNA sequencing
                Next-Generation Sequencing
                Biology and Life Sciences
                Computational Biology
                Genome Analysis
                Transcriptome Analysis
                Next-Generation Sequencing
                Biology and Life Sciences
                Genetics
                Genomics
                Genome Analysis
                Transcriptome Analysis
                Next-Generation Sequencing
                Biology and Life Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Rectum
                Medicine and Health Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Rectum
                Biology and Life Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Colon
                Medicine and Health Sciences
                Anatomy
                Digestive System
                Gastrointestinal Tract
                Colon
                People and Places
                Geographical Locations
                Africa
                Zimbabwe
                Custom metadata
                All relevant data are within the paper and its supporting information files. The variants described in this article have been submitted to the international mismatch repair variant database ( www.insight-group.org), and are available on https://databases.lovd.nl/shared/individuals/00247311; https://databases.lovd.nl/shared/individuals/00247312 and https://databases.lovd.nl/shared/individuals/00247314.

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