Handbook of Genetic Counseling/Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

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Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

Contracting[edit]

  • Introductions
  • What are your main concerns? What do you hope to learn today?
  • What do you know about colon cancer?

Review Family and Medical History[edit]

  • Medical History
    • How have you gotten to this point?
    • Screening practices?
    • Other significant illnesses, hospitalizations?
  • Family History
    • Other individuals with any type of cancer?
    • If affected:
      • Age and date at diagnosis, death
      • Current age
      • Type, location, stage of primary cancer
      • Secondary cancer - metastasis or new primary
      • Environmental exposures
    • If unaffected:
      • Current age
      • Health and history of illness
      • If deceased, cause and age at death
    • Screening practices
    • Family thoughts on cause of cancer?

Colon Cancer[edit]

  • Third leading cause of cancer in men and women
    • 9% of new cancer diagnoses, 11% of all cancer deaths
    • Incidence is over 130,000 new cases per year
    • About 5-10% of all colorectal cancers are hereditary
      • 3-5% due to HNPCC
      • 1% due to FAP
    • About 10-30% of colorectal cancers are familial
  • Caused by uncontrolled proliferation of cells in colon or rectum
    • Symptoms may include blood in stool, diarrhea, constipation, stomach cramps, frequent bloating, weight loss, or unusual and continuing lack of energy
    • Cancer cells may enter blood or lymphatic system and metastasize to form secondary tumors in other parts of body
  • Multifactorial disorder involving both genetic and non-genetic factors
    • Non-genetic factors
      • Diet: high fat, low fiber, high red meat intake
      • Colorectal polyps (adenomatous polyps)
      • Alcohol, cigarettes
      • Chronic disease of bowel (Crohn's disease, inflammatory bowel disease, ulcerative colitis)
      • Obesity
    • Genetic factors
      • Hereditary colorectal cancer syndromes
        • HNPCC and FAP
        • Rare colorectal syndromes: Peutz-Jeghers Syndrome, Juvenile Polyposis Coli
      • All cancers have genetic component but not all are hereditary

Genetic Etiology of Hereditary Colon Cancer[edit]

  • Autosomal dominant inheritance
    • Each child of mutation carrier has 50% chance of inheriting mutation
    • Mutations in DNA mismatch repair genes
      • MSH2 at 2p22
      • MLH1 at 3p21
      • PMS1 at 2q31
      • PMS2 at 7p22
      • MSH6 at 2p16
      • 60% of HNPCC due to mutations in MSH2 or MLH1
    • Carcinogenesis due to loss of heterozygosity of one of genes above
      • Causes defective mismatch repair
      • Mutations accumulate throughout the genome
    • Microsatellite instability (MSI)
      • Provides indirect evidence for presence or absence of germline mutation
      • Due to genome wide instability of replication and repair of repeat sequences
      • 10-15% of sporadic tumors show MSI, >95% of HNPCC tumors show MSI
  • Penetrance variable - use lifetime cancer risks for mutation carriers
    • Mutation also increases risk for other types of cancer besides colorectal cancer
    • 30% risk of second primary 10 years after original diagnosis
    • 50% risk of second primary 15 years after original diagnosis


Lifetime Risks for HNPCC-Related Cancers
Site Population Risk Hereditary Risk
Colon/Rectum 5% 70-80%
Endometrium 1.5% 60%
Ovarian 2% 9%
Urinary Tract (Kidney and Ureter) <1% 10%
Stomach <1% 19%
Small Intestine <1% <5%

Cancer Risk Assessment[edit]

  • Features of hereditary colorectal cancer
    • More than one generation affected
    • Early age at diagnosis
    • Bilateral or multiple primary cancers
    • Combination of tumors consistent with specific cancer syndrome
  • Strengths and limitations of cancer risk assessment
    • Knowledge of family history may be limited
    • Cancer occurs with or without hereditary cancer syndrome
    • Can't diagnose on the basis of family history information alone
  • Features associated with HNPCC
    • Polyps present in small numbers or not at all
    • Proximal (right-sided) colon cancer
    • Mean age at diagnosis is 45 years
  • Individual risk based on personal/family history: ________
  • Muir-Torre Syndrome
    • Variant of HNPCC
    • Associated with MSH2 or MLH1 mutations
    • Typical features of HNPCC
    • Also includes sebaceous gland tumors and keratoacanthomas
  • Turcot Syndrome
    • Rare hereditary syndrome of multiple colorectal adenomas and brain tumors
    • Two subtypes
      • APC mutations associated with medulloblastomas
      • MMR mutations associated with glioblastomas

Genetic Testing[edit]

  • Diagnostic/Testing Criteria for HNPCC
    • Amsterdam Criteria
      • Family must meet ALL of the following
        • Three cases of colorectal cancer
        • One affected person is first-degree relative of other two
        • Two successive generations affected
        • One diagnosis < 40 years
        • FAP excluded in cases of colon cancer
        • Tumors verified by pathology
      • Failure to meet these criteria DOES NOT exclude HNPCC
    • Modified Amsterdam Criteria
      • Family must meet ALL of the following
        • Three relatives with HNPCC-related cancer
        • One person is first-degree relative of other two
        • Two successive generations affected
        • One diagnosis < 50 years
        • FAP excluded in cases of colon cancer
        • Tumors verified by pathology
      • HNPCC-related cancers include colorectal, endometrial, small bowel, ureter, renal pelvis)
    • Bethesda Guidelines for eligibility for MSI testing
      • Family or proband meets at least one criteria
        • Family fits either Amsterdam criteria
        • Proband has two HNPCC-related cancers
        • Proband has CRC plus 1st degree relative with HNPCC-related cancer or CRC adenoma <45 years
        • Colorectal or endometrial cancer diagnosed before 45 years
        • Right-sided colon cancer if undifferentiated diagnosed before 45 years
        • Signet-ring cell type colorectal diagnosed before 45 years
        • Colon adenomas diagnosed before 45 years
      • If high MSI, proceed to germline mutation testing
  • Common adult cancers may be due to one of several genes or genetic and environmental interactions
    • Negative result difficult to interpret since it can be more than one gene
    • Preferable to identify mutation in relative with cancer before testing other at-risk relatives
    • General population screening not appropriate for this reason
    • DNA banking is option to defer testing until sometime in future
  • Testing procedures
    • Process
      • Blood drawn here and sent to outside lab (Myriad)
      • Results usually take about 4 weeks
    • Payment methods
      • Patient pay with check, money order, credit card
      • Insurance claims
        • Submit patient insurance authorization with sample
        • Requires 20% copay or insurance verified patient portion
      • Medicare claims - Medicare Waiver of Liability required
      • Institutional pay - Myriad bills institution directly
    • Current prices
      • Comprehensive COLARIS (MLH1 and MSH2 sequencing) $1950
      • Single Site COLARIS (known family mutation) $315
      • Micorsatellite Instability $600
        • Used to screen before DNA testing
        • Must be done on tumor tissue
        • Cannot be billed to insurance
    • Practice guidelines for testing
      • If positive for Bethesda criteria, start with MSI
      • If MSI high, consider genetic testing
      • If MSI low or negative, consider testing if Amsterdam positive
      • If Bethesda and Amsterdam negative, manage based on family history
  • Mutation identified
    • Increased risk for cancer
    • Gene could be passed on to children
    • Other at-risk relatives should be informed and offered counseling
    • Important to establish management plan
    • Insurance issues
  • Mutation not identified
    • Inherited cancer can't be ruled out since mutation may have been missed or exist in another gene
    • May be no genetic explanation for cancer in family
    • Person with cancer who does not have mutation may be sporadic case
    • Relatives may still be at risk and should discuss family history with their doctor
  • Limitations of testing
    • Can't predict when a person with a mutation will develop cancer
    • Not all persons with mutation will develop cancer
    • Some mutations may be missed or can't be interpreted
    • Efficacy of screening for some related cancers (e.g. ovarian) is unknown
  • Benefits of testing
    • May provide information
      • Explanation for cancer in family
      • Increased surveillance or plan for future
      • Clarify risks to children and other family members
    • Reassurance
    • Colon surveillance in at risk persons proven to reduce mortality
  • Risks of testing
    • Insurability
    • Employment issues
    • Confidentiality
    • May alter family relationships
    • Adverse psychological effects
      • Survivor guilt
      • Transmitter guilt
      • Depression
      • Anxiety
  • Not appropriate to offer testing for adult onset disorders for prenatal diagnosis or to anyone under age 18

Screening and Management Options[edit]

  • Screening guidelines
    • Colonoscopy
      • Starting at age 25 or 5-10 years before age of first colorectal cancer diagnosis
      • Repeat every 1-2 years
      • Surveillance decreases mortality by 65%, decreases CRC by 62%
      • Promotes early detection, improved survival
    • Endometrial and ovarian cancer
      • Transvaginal ultrasound, CA-125 levels starting 30-35 every 1-2 years
      • Endometiral biopsy annually starting at age 25
    • Stomach
      • If previous family member affected
      • Upper GI endoscopy every 1-2 years starting at age 30
    • Urinary tract
      • If previous family member affected
      • Ultrasound and urine cytology every 1-2 years starting at age 30
  • Prophylactic surgery
    • Effectiveness unknown so no recommendations for or against surgery
    • Does not eliminate cancer risk
    • Subtotal colectomy
    • Hyterectomy with or without oophorectomy
  • Chemoprevention
    • Current multicenter trial recruiting patients with known mutation or high MSI tumors and Amsterdam positive family history
    • No chemopreventive therapies for HNPCC.
    • NSAIDs can reduce number of adenomas in FAP and may work for HNPCC too

Psychosocial Issues[edit]

  • Motivation for undergoing testing
    • Decision-making about testing, surveillance, and prevention
    • Stress level, previous experiences with cancer
  • Reactions to positive, negative, and uninformative results
    • Changes in medical management
    • Who else will be told about results
  • Family, social support system

Resources[edit]

  • IMPACC (Intestinal Multiple Polyposis and Colorectal Cancer
PO Box 11
Conyngham, PA 18219
(717) 788-1818
  • American Cancer Society
National Headquarters
1599 Clifton Road, N.E.
Atlanta, GA 30329
(800) ACS-2345
  • Hereditary Colorectal Cancer Registry
The Johns Hopkins Hospital
550 North Broadway, Suite 108
Baltimore, MD 21205-2011
(410) 955-3875

References[edit]

  • Everett, J. "Hereditary Non-Polyposis Colorectal Cancer." Genetic Counseling and Cancer lecture (2002).
  • "Identifying and Managing Risk for Hereditary Nonpolyposis Colorectal Cancer and Endometrial Cancer (HNPCC)." American Medical Association (2001).
  • "Module 6: Hereditary Colorectal Cancer Syndromes." OncoSep 43-55.
  • "The Johns Hopkins Guide for Patients and Families: Hereditary Nonpolyposis Colorectal Cancer." The Johns Hopkins University (1995).

Notes[edit]

The information in this outline was last updated in 2002.