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Part Two. Welcome back. Familial Cancer Genetics. Cancer Genetics. 5-10% of all cancer clearly linked to an inherited gene alteration If cancer seen at younger ages (before 50) possible that inherited genes increased susceptibility

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Part Two

Welcome back


Familial Cancer Genetics


Cancer Genetics

  • 5-10% of all cancer clearly linked to an inherited gene alteration

  • If cancer seen at younger ages (before 50) possible that inherited genes increased susceptibility

  • Some genetic conditions increase someone’s risk of getting several different types of cancer at young age (eg. Li-Fraumeni syndrome, MEN 1)

  • Some gene alterations lead to uncontrolled cell growth:

    • tumour suppressor genes

    • oncogenes

    • DNA repair genes


Breast Cancer

  • BRCA 1 & BRCA 2 testing may be available for people at high risk, but others genes known to be involved

  • If gene alteration found, woman at up to 80% lifetime risk of developing breast cancer

  • Carry risk of other cancers; ovary (BRCA 1 = 44%, BRCA 2 = 27%), and a slightly increased risk prostate, pancreas and some other cancers

  • Dominantly inherited through families (ie. only one copy of the altered gene needed for it to have effect)


AUTOSOMAL DOMINANT INHERITANCE

Parents

Gametes

At conception

Unaffected

Affected


Hereditarygene alteration

1 Somatic mutation

Somatic mutation

Cancer

Normal Tissue


Hereditarygene alteration

Somatic mutation

2 Somatic mutations

Cancer

Cancer


What would indicate that a woman is at higher risk of developing breast/ovarian cancer?

Relative with breast cancer before the age of 40

Relative with bilateral breast cancer

Relative with male breast cancer

2+ relatives on the same side of the family affected by breast cancer (especially if affected at younger ages)

2+ relatives with ovarian cancer


Breast Cancer Referral


  • Low risk – manage in primary care

  • Older age of onset

  • Different sides of the family

Case 1

Breast cancer

65

70

76

46

Kay

49

51

53

55

Reassure and explain population risk. Advise on symptom awareness and to report any changes in family history


Ovarian Cancer


  • Refer – high risk

  • Young age onset

  • Equal transmission through men

  • Multiple tumours in one individual

  • Breast and ovarian cancer

Case 2

42

48 breast cancer

56 ovarian cancer

Breast cancer

Ovarian cancer

32

Janet


Colorectal Cancer

Familial Adenomatous Polyposis (FAP)

Hereditary Non-Polyposis Colorectal Cancer

(HNPCC).

Other cancers associated with

HNPCC – endometrial, stomach,

ovarian

Supporting Genetics Education for Health

www.geneticseducation.nhs.uk


Bowel Cancer

HNPCC related cancers include endometrial, gastric,

ovarian, pancreatic and urothelial


Case 3

35

died in war

68

73

60’s

77

78

73

75

43

Colorectal cancer

32

Peter

Refer – moderate risk Young age of onset (under 45)


Case 4

Colorectal

cancer

Endometrial cancer

55

69

49

42

George

80

75

48

78

Refer – High risk

Young age of onset,

Endometrial and Bowel

Two generations, Polyps

39

Polyps

30

Martin

42


Referral for family history of cancer

  • Young age at onset,

  • Pattern of similar tumours on one side of the family (or multiple primaries in one individual)

  • Use national/local guidelines e.g. NICE familial breast cancer

  • Remember ethnicity e.g. – Chinese, Indian, Ashkenazi Jewish ancestry

  • If in doubt - Contact the Clinical Genetic Service


Patient Information

  • Detailed information of affected family members required

  • Patient will receive information regarding level of risk and options

  • Will not necessarily mean a genetic test


AUTOSOMAL DOMINANT INHERITANCE

Parents

Gametes

At conception

Unaffected

Affected


Familial Hypercholesterolaemia

  • If fulfil Simon Broome criteria, refer to specialist lipidologist

  • Where Genetic testing is not available, cascade testing for family members by fasting lipid profile

  • Children tested below 10 years

  • Boys have lower cholesterol during puberty


Heart UK Definition using Simon Broome Register

Definite Familial Hypercholesterolaemia:

PLUS

b) Tendon xanthomas in patient, or in 1st degree relative (parent, sibling, child), or in 2nd degree relative (grandparent, uncle, aunt)

OR

c) DNA-based evidence of an LDL receptor mutation or familial defective apo B-100


Heart UK Definition using Simon Broome Register

Possible Familial Hypercholesterolaemia:

PLUS

  • d) Family history of myocardial infarction: below age of 50 in 2nd degree relative or below age 60 in 1st degree relative

    Or

  • e) Family history of raised cholesterols:

    • >7.5 mmol/l in adult 1st or 2nd degree relative or

    • > 6.7 mmol/l in child or sibling under 16


X-LINKED INHERITANCE WHERE THE MOTHER IS A CARRIER

Father

Mother

Parents

(Unaffected)

(Carrier)

Gametes

X

Y

X

X

At conception

Son

Daughter

Daughter

Son

(Affected)

(Carrier)


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