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Introduction to Cancer Genetics PowerPoint Presentation

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Description : This medical presentation on cancer titled "Introduction to Cancer Genetics" provides us an overview on cancer syndromes and management options, genes and genetic testing, genetic counselling and cancer genetic service, and population cancer risk.

Tags : Cancer, Introduction, Cancer Genetics, syndromes, management, genes, genetic testing, genetic counselling, genetic service, risk, Sporadic Cancer, Breast and ovarian, Colon cancers, Cowden syndrome, Gastric cancer, Gorlin Syndrome, Li-Fraumeni, Multiple endocrine neoplasia, Neurofibromatosis, Peutz-Jeghers syndrome, Phaeochromocytoma Retinoblastoma, von Hippel-Lindau disease, Wilm’s tumour

Published on : May 03, 2021 | Views : 3010 | Downloads : 7

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Slide 1-

Introduction to Cancer Genetics Emma Williams Genetic Counsellor NE Thames Regional Genetics Service
Slide 2-

Overview Population cancer risk Genetic Counselling & Cancer Genetic Service Genes & Genetic testing Cancer Syndromes & Management options
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What are the cancer risks for the general population? 1 in 3 people will develop cancer at some point in their lives Prostate: 17% Female Breast: 12-13% Lung: 6-8% Colorectal cancer: 6% Melanoma: 1-2% Ovarian: 1.5% Stomach / Pancreas: 1% Male breast: 0.1% SEER Figures. NCI 2001-2003
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How Many Cancers are Genetic? Sporadic (~85%) Familial (~10%) Hereditary (~5%)
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Sporadic Cancer Many patients may have a similar FHx Age of diagnosis typically later in life Usually not inherited Can be reassuring
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Aims of Genetic Counselling Help patients to… Understand the information about the genetic condition Appreciate inheritance patterns and risk of recurrence Understand available options Make informed choices appropriate to their personal and family situation Make the best possible adjustment to the condition and risk
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Do Genes Affect Cancer Risk?
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Risk Assessment Tools Referral guidelines / NICE guidelines Family History form Comprehensive 3 generation pedigree Confirmation of cancer pathology Pedigree assessment Manchester score BOADICEA (Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm) Amsterdam I/II Criteria Bethesda Criteria
Slide 9-

Genetic Cancers Breast and ovarian Colon cancers Cowden syndrome Gastric cancer Gorlin Syndrome Li-Fraumeni Multiple endocrine neoplasia (MEN) Neurofibromatosis Peutz-Jeghers syndrome Phaeochromocytoma Retinoblastoma von Hippel-Lindau disease Wilm’s tumour
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Hereditary Cancer Several affected family members Earlier than average age of onset Multiple generations are affected on one side of the family A particular pattern of cancers noted Individuals with more than one primary tumour site 5-10% of Cancer Cases
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Most Cancer Susceptibility Genes Are Dominant With Incomplete Penetrance You only need one altered copy of the gene to have an increased risk of cancer Gender is irrelevant It is not possible to “skip” generations Penetrance can be incomplete All offspring are at 50:50 risk Normal Carrier, affected Ca Sporadic Ca Susceptible Carrier
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Genetic Testing Genetic testing is usually carried out on DNA from a blood sample Technically difficult to locate the mutation in a cancer gene for a particular family Can take up to three months Usually need to first test a living relative who has already developed cancer Is only offered to high risk families (>20% chance of mutation) Often cannot locate a mutation in a family (only identified in about 20% of families)
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Genetic Testing cont… Genetic testing is NOT usually possible if there are no living affected relatives Exception is populations with founder mutations eg Ashkenazi Jewish population Once a mutation is found, testing can be offered to other at-risk family members Individuals who DO NOT carry the family mutation ARE NOT at increased risk of developing the cancers, but are still at population risk Individuals who DO carry the family mutation ARE at increased risk of developing cancer but there is still uncertainty. . . However, testing enables us to identify individuals who may be at higher risk of developing certain types of cancer
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Hereditary Breast and Ovarian Cancer Most cases caused by a mutation in BRCA1 or BRCA2 gene BRCA1 / 2 are tumour suppressor genes, which are involved in the repair of DNA Accounts for about 5% of breast cancer cases and about 12% of ovarian cancer cases Accounts for 4-5% breast cancer cases 40-70% lifetime risk breast cancer 10-45% lifetime risk ovarian cancer Increased risk prostate cancer in male carriers Genetic testing possible for some families Surgery and surveillance options for affected individuals BRCA1 BRCA2 5-10% Other genes Sporadic Hereditary
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BRCA1 -Associated Cancers: Lifetime Risk Increased risk of other cancers, eg about double population risk for prostate cancer in men Breast cancer 56%-87% (often early age at onset) Second primary breast cancer 64% Ovarian cancer 16%-44%
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BRCA2-Associated Cancers: Lifetime Risk Other cancers: pancreatic malignant melanoma breast cancer (50%-80%) ovarian cancer (15-27%) male breast cancer (7%) contralateral breast (50%) prostate (~30%)
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Options for BRCA1/2 Carriers Cancer Screening Additional breast screening by mammography / MRI Ovarian screening through UKFOCSS research trial Prophylactic bilateral mastectomy ~90% reduction in breast CA risk Prophylactic bilateral salpingo-oophorectomy ~up to 96-98% reduction in ovarian CA risk ~50% reduction in breast CA risk (age dependant) ? Chemoprevention in the future ? Tailoring of treatment for carriers in the future
Slide 18-

When to refer 2 first or second degree relatives with breast cancer < 50 yr 3 first or second degree relatives with breast cancer <60yr 4 relatives with breast cancer at any age 1 ovarian cancer at any age + 1 breast cancer < 50yr 1 ovarian cancer + 2 breast cancer both < 60y 2 ovarian cancer any age Patients who are thought to be of Ashkenazi Jewish heritage with at least one first degree relative with breast cancer <50 years or ovarian cancer any age NB bilateral breast primaries equivalent to 2 relatives
Slide 19-

Colorectal Cancer
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HNPCC or Lynch syndrome Hereditary non-polyposis colorectal cancer (HNPCC) 3-5% of all colorectal cancer cases Autosomal dominant – multiple generations affected High penetrance Typical age of CA onset is 40-50 yrs 60-70% right-sided/proximal CRC tumors Polyps may be present, multiple primaries common. Can overlap with AFAP
Slide 21-

HNPCC Lifetime cancer risks: Colorectal 80% Endometrial 20-60% Gastric 13-19% Ovarian 9-12% Biliary tract 2% Urinary tract 4% Small bowel 1-4% Brain/CNS 1-3%
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HNPCC Caused by mutations or deletions in mismatch repair (MMR) genes MMR genes are like spell checkers in our DNA. MSH2, MLH1, MSH6, PMS2 90% of detectable mutations in MSH2 and MLH1 7-10% of detectable mutations in MSH6
Slide 23-

Options for individuals with HNPCC 1-2 yearly colonoscopy Ovarian and endometrial screening (not proven to be effective) ? renal/upper GI screening effective (if have history of gastric/renal cancers) Surgery Prophylactic bowel surgery not often chosen Total abdominal hysterectomy and salphingo oophorectomy for females
Slide 24-

Familial adenomatous polyposis (FAP) 1 in 10,000 incidence 100’s to 1000’s of colonic adenomas by teens 7% risk of CRC by 21 yrs; 93% by 50 yrs 20-25% no history in parents Extra-colonic features Screening 1 – 2 yearly flexible sigmoidoscopy from age 10 – 12 Upper GI endoscopy 1 –3 yearly from age 25
Slide 25-

MAP syndrome/MYH gene MYH associated Polyposis (MAP) syndrome Autosomal recessive; mutations in the MYH gene Median number of polyps = 55 Mean age of polyp diagnosis = 30-50 years Polyps mainly small, mildly dysplastic tubular adenomas. Some tubulovillous, hyperplastic, serrated adenomas, microadenomas 30% of individuals with 15-100 polyps have homozygous mutations in the MYH gene Genetic testing should be offered if >10-15 polyps (and APC gene testing negative)
Slide 26-

When to refer Patient or 1 first degree relative affected with Colorectal cancer <50yrs 2 or more colorectal primary cancers any age Colorectal cancer and a related cancer* any age. 2 first degree relatives affected with colorectal cancer or related cancer* at any age 3 relatives affected with colorectal cancer or related cancer* at any age, one of which must be a first degree relative. History of Polyposis (e.g. Familial adenomatous Polyposis) *related cancers- endometrial, ovarian, small bowel, ureter, renal pelvis and stomach
Slide 27-

Genetics and Uncertainty Cancer genetics is not relevant for most people Cancer genetics is not a crystal ball But cancer genetics can have a great impact on those families most at risk of familial cancer
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What Can You Do? Recognise patterns of cancers in families Young onset Lots of one or two particular types of cancer Jewish? If not sure ask Don’t be afraid to contact genetics for advice Take a blood sample for DNA banking
Slide 29-

DNA Banking DNA banking provides families with the chance to pursue genetic testing at a later point in time. where there is currently no genetic test available. DNA banking will allow the family to take advantage of future advances in genetic testing technology. A family member diagnosed with cancer who is terminally ill and there is no time for traditional a genetic assessment and/or testing. The family can then focus their attention on their loved one and defer the process of genetic counselling and testing to a time when they are ready.
Slide 30-

Contact Details Emma Williams Registered Genetic Counsellor NE Thames Regional Genetics Service Great Ormond Street Hospital Great Ormond Street London, WC1N 3JH email: emma.williams@gosh.nhs.uk Tel: 0207 905 2625 Fax: 0207 813 8141
Slide 31-

Case 1: Ruth Ruth, a 35 year old Ashkenazi Jewish woman, comes because she is anxious about her family history of cancer. You inquire about family health history and find out the following information: Paternal family history is as follows: Paternal grandmother diagnosed with ovarian cancer age at 63 Paternal aunt diagnosed with breast cancer age 42 Ruth has no other risk factors or pertinent family history
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Case 1: Pedigree Key -Ov Ca -Br CA Dx 63 82 yrs Ruth 35 Russian Jewish Polish Jewish 41 38 60 58 Dx 42 64yrs
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Case 1: Assessment Patient is in “Moderate risk” category However ethnicity is important as she is of Ashkenazi Jewish descent Refer to genetics clinic Moderate risk screening for breast cancer arranged Genetic testing for 3 common ‘Jewish Mutations’
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Case 2: Ann Ann has come along because her sister has ovarian cancer, sadly the cancer has spread. Her family history is a follows: Sister diagnosed with ovarian CA at 53 yrs. Mother diagnosed with ovarian CA at 61 yrs and has sadly died. Maternal aunt diagnosed with breast cancer at 48 yrs. Ann has no other risk factors for breast cancer. She feels that with her family history, cancer is inevitable
Slide 35-

Case 2: Pedigree 2 49 DX 53 Dx 61 Died 64 2 3 30s 39 Dx 48 73 65
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Case 2: Assessment Patient is in “High” risk category Refer to genetics clinic promptly High risk screening breast and ovarian cancer Genetic testing offered
Slide 37-

Case 3 Helen has primary ovarian cancer Would this family need seeing by genetics? What other cancer could she be at risk for? YES Colon and uterine cancers
Slide 38-

Case 4 Key: Endometrial CA Colorectal CA Adenomatous polyps Dx 38 Dx 50 88 yr 63 yr 4 polyps 50 yrs. CRC Dx 48 61 yr 38 yr 10 yr 8 yr 35 yr French, Irish, Scottish German, English Lynch syndrome
Slide 39-

Case 5 Would you refer this gentleman to genetics? What else would you ask about the family? YES Is he Jewish? He has a BRCA mutation!
Slide 40-

Case 6 Which side of the family are you worried about? What surveillance does she need? Both Breast and ovarian screening She actually had two BRCA mutations!
Slide 41-

Case 7: Ted Ted is 30 and wants a colonoscopy because his mother was just diagnosed with colon cancer after routine screening at age 54. Family history reveals: Paternal grandfather: died of CRC at age 79. No hx of endometrial, ovarian, small bowel or ureter/kidney cancer on either side of family. Two maternal aunts: cervical cancer at ages 30 & 34 Maternal grandmother: breast cancer age 85 Reassure
Slide 42-

Case 8: Alison Alison is a 40 year old Caucasian (non-Jewish) patient who asks you for information about the “breast cancer gene test”. She states she wants this test. You ask about her family history: Mother with breast cancer - age 58 Maternal aunt with breast cancer – age 65 Paternal grandmother with breast cancer – age 79 Alison has no other risk factors for breast cancer She feels that with her family history, breast cancer is inevitable
Slide 43-

Case 8: Pedigree Dx 58 65 yr Dx 65 71 yr Dx 79 d.81 German/Dutch British Key: -Breast CA Alison 40 yr 15 yr
Slide 44-

Case 8: Assessment Patient is in “Moderate” risk category Refer to breast clinic for breast cancer screening from 40-50 years then NBSP Counselling issues: Unlikely to be due to a BRCA1 or BRCA2 mutation Screening and preventive strategies Psychosocial – perceived risk, fears Support resources