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Clinical Genetics > Clinical Cancer Genetics > Flashcards

Clinical Cancer Genetics Flashcards

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1
Q
  1. What can we do to reduce cancer risk in people at increased genetic risk?
A

Screening, Prevention, Early Detection

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2
Q
  1. Define DNA?
A

A molecule which contains the human genetic code

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3
Q
  1. What is the function of genes?

How many are in the human body?

A

o The instructions to tell the body how to grow, develop and function – translated into proteins.
o ~ 20,000 genes in the human genome with 2 copies of most genes – one on each chromosome

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4
Q
  1. How many bases in the entire human genome

Where is the entire length of DNA contained in?

A

•The human genome (3 billion bases)

The entire length of DNA contained in human cells.

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5
Q
  1. Approx how many genetic changes are there between two unrelated people?
A

•We have around 5 million different genetic changes compared to another unrelated person –> Genetic Variation

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6
Q
  1. List some cancer statistics:
    - Lifetime risk
    - % that is sporadic, familial and high risk genes
A
  • Cancer is a common disease in humans: There is a 1 in 2 lifetime risk of developing cancer.
  • 65% sporadic, 25% familial and 10% high risk genes.
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7
Q
  1. Most cancers are sporadic , what does this mean?
A
  • Most cancers are “sporadic” – due to acquired (somatic) mutations within a cell giving it a growth advantage
  • Acquired mutations in cancer genes “drive” the cell to become cancerous.
  • Repair mechanisms, carcinogens etc.
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8
Q
  1. What is an inherited cancer risk?
A 
•Some genetic changes we are born with may influence our lifetime cancer risk
o	High (cancer predisposition genes), moderate and low risk changes. 
o	E.g. multifactorial breast cancer (common).
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9
Q
  1. What is more common :
    - High risk cancer predisposition genes
    - Low risk cancer predisposition genes?
A
  • High risk cancer predisposition genes are rare.

* Low risk genetic changes are more common but only increase cancer risk by a little.

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10
Q
  1. How can we use GWAS to see a patients risk of developing cancer?
A

•Compare single nucleotide polymorphisms (SNPS) in cases and controls to see the likelihood of developing cancer.

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11
Q
  1. What is a polygenic disease?
A

A genetic disorder that is caused by the combined action of more than one gene.

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12
Q
  1. How does having a polygenic disease affect your risk of developing cancer?
A

•Presence of common variants shifts the normal distribution of developing cancer to the right (higher risk).

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13
Q 
13. For the following cancers list the associated high risk cancer predisposing gene that goes with it and the % of 
•	Breast cancer		
•	Ovarian 			
•	Colon 			
•	Melanoma			
•	Medullary thyroid		
•	Retinoblastoma		
•	Prostate			
•	Pancreatic
A

Breast cancer 5-10% BRCA

Ovarian 10% BRCA

Colon 5-10% Lynch

Melanoma 10% CDKN2A

Medullary thyroid 25% RET

Retinoblastoma 40% RB1

Prostate 5-10% BRCA2

Pancreatic 10% BRCA2

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14
Q
  1. What different approaches are there for assessing inherited cancer risk?
A

-> 3 generations of family history assessment
and look out for :
• Bilateral (pair of organs) cancer or multiple cancers in the same individual.
• Young age of onset e.g. breast cancer under the age of 40.
• Multiple cancer diagnoses of same type in closely related individuals (number, type and how closely related)
• Multiple cancer diagnoses of cancers related to specific CPG in closely related individuals

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15
Q
  1. What are certain pathological subtypes of cancers most likely to be due to?
    - Give some examples?
A

High risk CPG (cancer predisposing genes)
o High grade serous ovarian cancer: BRCA1/2
o Medullary thyroid cancer: RET
o Triple negative breast cancer: BRCA1/2
o Type 2 papillary kidney cancer: FH

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16
Q
  1. What kind of molecular tests would we do on a tumour?
A

sequencing shows genetic changes which could indicate inherited risk – need to check with a blood test e.g.
o Immunohistochemistry of mismatch repair genes in Lynch Syndrome.
o BRCA gene sequencing in ovarian cancer

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17
Q
  1. What are two syndromic features of cancer and what cancers can they be a sign on?
A 
o	Trichilemmoma (skin legions – increased risk of thyroid, breast and womb cancer).
o	Musculocutaneous pigmentation (increased risk of cancer and bowel polyps).
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18
Q
  1. What kinds of decisions need to be made on assessment of cancer?
A

• Is there an increased inherited risk of cancer and how high is it?
• Does the patient need genetic testing to look for high risk cancer predisposition genes?
o Usually around a 1 in 10 chance of finding a mutation in a high risk cancer predisposition gene.
• Does the patient and/or their relatives need extra screening or other measures to reduce cancer risk?

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19
Q
  1. Where would you find the criteria that needs to be met to decide whose offered genetic testing?
A

National Genomic Test Directory

20
Q
  1. What type are most cancers
    - Sporadic
    - Inherited genetic changes
A
  • Most cancers are sporadic due to acquired (somatic) mutations which occur only in the cancer cell
  • A smaller proportion of cancers occur due to inherited genetic changes
21
Q
  1. What two types of inherited genetic changes are there?
A

o These can be multiple lower risk genetic variants – this is known as multifactorial or polygenic risk
o Or a single high risk genetic variant in a cancer predisposition gene

22
Q
  1. Summarise how you would asses for an inherited cancer risk?
A

o Take a 3 generational family history:
– Ages, types of cancer and number of affected relatives.
– Ethnic origin – higher rate of CPG in some populations.
o Consider the types of cancer in detail to see if they increase the chance of a high risk cancer predisposition gene (CPG).
o Look for any rare syndromic features which could indicate a high risk cancer predisposition gene.
o Use the National Genomic Test Directory Eligibility Criteria to decide if genetic testing is indicated.

23
Q
  1. In multifactorial or polygenic cancers, what % chance is there of CPG or gene testing being negative?
A

<10% chance of CPG or gene testing is negative

24
Q
  1. How can we manage inherited cancer risk?
A

•Offer screening, prevention and early detection advice (SPED) – use algorithms to work out who has moderate risk (mammograms every 3 years) and who has high risk (annual mammograms) to decide how they are screened.

25
Q
  1. How does chemoprevention work?

- What is an disadvantage

A

o Taking a medication to reduce cancer risk e.g. tamoxifen/SERM for breast cancer or aspirin for colorectal cancer.

Disad = May have side effects on quality of life

26
Q
  1. What are some considerations that need to thought about when doing a genetic test for High risk CPGs?
A

Implications for individual: Recurrence risks or Risks of other cancers
o Implications for relatives
– How to share information
– Concerns about children
– Family planning options (e.g. prenatal, PGD)

27
Q
  1. What is the difference between diagnostic AND predictive testing?
A
  • Diagnostic testing: To confirm whether a CPG has caused the cancer.
  • Predictive testing: To identify if an unaffected person carries a CPG
28
Q
  1. Does healthcare insurance cover predictive testing?
A

Current moratorium (ban) for predictive testing

29
Q
  1. What is the next steps if no genetic variants are identified in tests (most likely outcome, 90% of cases)?
A

o Screening and management on personal and family history
o Referral for screening/further management only if indicated on above assessment
o Reassuring for patient but reiterate participation in population screening programmes

30
Q
  1. What is the next steps if a disease causing variant in a CPG is found (rare-10% of cases)
A

o Screening and management tailored to specific CPG

o Should be reviewed by NHS clinical genetics service

31
Q
  1. What should be the next steps if the outcome of genetic testing is that a variant of uncertain significance (VUS) is found?
A

o Benign until proven guilty
o Referral for screening/further management only if indicated on above assessment
o May be anxiety provoking for patient - Need to understand how common genetic variation is

32
Q
  1. For both SPORADIC and HEREDITARY cancers, what is the likelihood of getting other cancers or recurrence of that cancer?
A

Hereditary :
-High risks of recurrence/other associated cancers

Sporadic:
-No increased risk of other cancers

33
Q
  1. For both SPORADIC and HEREDITARY cancer what is the risk of cancers in relative?
A

Hereditary :
-High cancer risks in relatives

Sporadic:
-Usually small increased risk of cancer in relatives

34
Q

34 . For both SPORADIC and HEREDITARY cancer, what type (if any) genetic testing takes place

A

Hereditary:
Offer testing to at risk individuals and screening/preventative management to gene carriers.

Sporadic:
No genetic testing indicated.

35
Q
  1. For both SPORADIC and HEREDITARY what differences would there be in treatment / clinical management is there?
A

Hereditary:
•May have alter treatment of affected individuals.

Sporadic:
•Normal clinical management for affected individuals.

36
Q
  1. Compare somatic and germline mutations?
A

Somatic :

  • occur in nongermline tissue
  • Cannot be inherited
  • Mutation in tumour (eg breast )

Germline:

  • Present in egg and sperm
  • Can be inherited
  • Cause cancer family syndrome
  • Mutation in egg or sperm –> All cells affected in the offspring
37
Q
  1. What type of cancer is breast cancer associated with?
A

Ovarian cancer

38
Q
  1. When there is a mutation in the BRCA1 gene, what risks are there in UNAFFECTED carriers?
    Give the chance % of getting that cancer
A
  1. Breast Cancer (lifetime risk to 80yrs) 60-90% chance
  2. Ovarian Cancer (lifetime risk: mainly after 40) 40-60%
  3. Male Breast Cancer (lifetime risk) 0.1-1.%

4.Prostate Cancer
(Lifetime risk similar to population risk) 8%

39
Q
  1. When there is a mutation in the BRCA1 gene, what risks are there in AFFECTED carriers?
    Give the chance % of getting that cancer
A
  1. Women with unilateral breast cancer (lifetime risk of contralateral breast cancer) -50%
    Overall 5 year risk - 10%
40
Q
  1. When there is a mutation in the BRCA2 gene, what risks are there in UNAFFECTED carriers?
    Give the chance % of getting that cancer
A
  1. Breast Cancer (lifetime risk to 80yrs) 45-85% chance
  2. Ovarian Cancer (lifetime risk, mainly after 50) 10-30%
  3. Male Breast Cancer (lifetime risk) 5-10%

4.Prostate Cancer
(Lifetime risk ) 25%

41
Q
  1. When there is a mutation in the BRCA2 gene, what risks are there in AFFECTED carriers?
    Give the chance % of getting that cancer
A
  1. Women with unilateral breast cancer (lifetime risk of contralateral breast cancer) -50%
    Overall 5 year risk - 5-10%
42
Q
  1. What kind of surveillance is needed for
    - Breast Cancer
    - Ovarian Cancer
    - Other Cancers
A

Breast:

  • Advise on breast awareness
  • Annual mammography from 40-70
  • Annual MRI from 30-50
  • No breast surveillance for male carriers

Ovary:
-Ovarian Surveillance is not recommended

Other Cancers:

  • No surveillance is recommended for other cancers
  • Carrier might be used for research
43
Q
  1. Is Chemoprevention suitable for BRAC1 or BRAC2 mutation carriers?
A

BRAC1 carriers:
-Not suitable

BRACA2:

  • Discuss benefits and side effects
  • Can be offered if no contra-indications
44
Q
  1. What risk reducing surgery can be done to reduce breast cancer?
A
  • Bilateral risk-reducing mastectomy

- Breast cancer risk reduction 90-95%

45
Q
  1. What risk reducing surgery can be done to reduce ovarian cancer as well as breast cancer
    what are some side effects
    what is a medicine alternative?
A
  • Bilateral salpingo-oophorectomy (remove ovary and fallopian tubes) once childbearing is complete
  • Reduces risk of ovarian cancer by 95%
  • Reduces risk of breast cancer by 50%
  • Side effect : premature menopause
  • HRT should be offered to women until 50 in women who have not had ER positive breast cancer
46
Q
  1. The management of cancer depends on the risk level :

- What kind of management would you need for moderate - high risk?

A

– Screening and early detection mainstay of management and chemoprevention as risk increases

47
Q
  1. The management of cancer depends on the risk level :

- What kind of management would you need for high risk cancer predisposition genes?

A

– Gene specific guidelines: Screening, Chemoprevention and Surgical management

Clinical Genetics (5 decks)

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