Transcript ASCO_2009_files/Lynch Educat MSI ASCO 2009

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PRACTICAL ASPECTS OF
ASSESSING MSI STATUS: WHAT
TESTS TO ORDER AND HOW TO
INTERPRET THEM
by
HENRY T. LYNCH, M.D.
JANE F. LYNCH, B.S.N.
CARRIE SNYDER, R.N, M.S.N.
Creighton University
School of Medicine
Omaha, Nebraska
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Magnitude of the Problem
Annual worldwide incidence of CRC is 1,023,152*:
• Lynch syndrome (LS) accounts for  2-5%
(20,460-51,160 cases).
• < 1% (10,230 cases) constitute FAP.
•  20% (204,630 cases) are familial (2 or more firstdegree relatives with CRC.
*International Agency for Research on Cancer.
Globocan 2002. Available at: http://www-dep.iarc.fr/.
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Magnitude of the Problem
Question: Why are these figures of such
significant public health impact?
Answer: Each hereditary cancer comes from a
family that could benefit immensely from genetic
counseling.
DNA testing, surveillance, and highly-targeted
management are the key!
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J Clin Oncol25:3534-3542, 2007.
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Who Should Be Tested?
1. Pedigree consistent with hereditary colorectal
cancer (CRC) syndrome;
2. Known germline mutation predisposing to
cancer;
3. Patients at acceptable high cancer risk status;
4. Presence of cancer syndrome stigmata
(phenotype): e.g., polyposis in FAP;
5. Genetic counseling, risks/benefits understood;
6. Consent given;
7. Results: full explanation of
surveillance/management advice.
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Who Should Be Tested?
Referral to medical geneticist/center of
hereditary cancer expertise:
1. When physician lacks expertise, referral should
be made to a cancer genetics center.
2. Key medical/genetic/genealogic findings made
available to referral center.
3. Patient/family acceptance.
4. Candidate for DNA testing accepts, is tested,
and results are fully explained in genetic
counseling setting.
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Could this be
hereditary
Colon Cancer
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LYNCH SYNDROME
HETEROGENEITY
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Cardinal Features of Lynch Syndrome
• Family pedigree shows autosomal dominant inheritance pattern for syndrome
cancers.
• Earlier average age of CRC onset than in the general population:
- Lynch syndrome: 45 years;
- general population: 63 years.
• Accelerated carcinogenesis, i.e., shorter time for a tiny adenoma to develop into
a carcinoma:
- Lynch syndrome: 2-3 years;
- general population: 8-10 years.
• High risk of additional CRCs:
25-30% of patients who have surgery for a LS-associated CRC will have a
second primary CRC within 10 years, if surgery was < a subtotal colectomy.
• Increased risk for certain extracolonic malignancies:
- endometrium (40-60% lifetime risk for ♀ carriers);
- ovary (12% lifetime risk for ♀ carriers);
- stomach (higher risk in families from Orient);
- small bowel;
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Cardinal Features of Lynch Syndrome
•
Increased risk for certain extracolonic malignancies (continued):
- hepatobiliary tract;
- pancreas;
- upper uroepithelial tract (transitional cell carcinoma of the ureter and renal
pelvis);
- brain (in Turcot’s syndrome variant of LS);
- sebaceous adenomas, sebaceous carcinomas, multiple keratoacanthomas
(in Muir-Torre syndrome variant of LS).
• Differentiating pathology features of LS CRCs:
- more often poorly differentiated;
- excess of mucoid and signet-cell features;
- Crohn’s-like reaction;
- significant excess of infiltrating lymphocytes within the tumor.
• Increased survival from CRC.
• Sine qua non for diagnosis is identification of germline mutation in MMR gene (most
commonly MLH1, MSH2, MSH6) segregating in the family.
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Familial
Hereditary
Sporadic
AC-1 without MMR
(Familial CRC of
syndrome “X”)
FAP; AFAP
Mixed Polyposis Syndrome
Ashkenazi I1307K
CHEK2 (HBCC)
MYH
TGFBR1
PJS
FJP
CD
BRRS
Hamartomatous
Polyposis
Syndromes
= as yet undiscovered
hereditary cancer variants
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Genetic Heterogeneity in HNPCC
MSH6
MSH2
MLH1
PMS2
PMS1
Chr 7
Chr 3
Chr 2
HNPCC is associated with germline mutations in
any one of at least five genes
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Lynch Syndrome: Genotypic Heterogeneity
Clinical cancer phenotypes differ with each of
the MMR mutations:
1. MSH2 has  extracolonic cancer types and
 Muir-Torre syndrome
2. MLH1 may have  CRC expression.
3. MSH6 may be more “benign” with  CRC but
 endometrial cancer.
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PMS2 Mutations, Phenotype, and Penetrance*
PMS2 mutations contribute significantly to LS.
Penetrance for monoallelic mutation carriers
appears to be lower than that for other MMR
genes.
*Senter et al. Gastroenterology135:419-428,2008.
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Valle et al. Science 321:1361-1365, 2008.
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Expression of TGFBR1 in CRC
Valle et al.* hypothesize that TGFBR1 is a notable
candidate for a gene that, when mutated, causes
predisposition to CRC.
It also acts as a modifier of other genes, resulting in
a predisposition.
*Science 321:1361-1365, 2008
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Molecular Genetics and Lynch Syndrome
15% of all CRCs show MSI:
Most not caused by Lynch syndrome.
Acquired silencing (epigenetic inactivation)
of MLH1 gene by methylation of promoter.
 Immunohistochemistry (IHC) useful for
identifying protein loss (MSH2, MLH1).
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Molecular Diagnosis of LS: Toward a
Consensus
If tumor is MSI-positive, IHC is then done to direct
mutational testing to a specific MMR gene, which MSI
alone cannot do.*
If tumor is MSS, must weigh low probability of an
informative IHC test and cost of performing it.**
*Engel et al. Int J Cancer 118:115-122, 2006.
**Lynch et al. J Natl Cancer Inst 99:261-263, 2007.
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Molecular Diagnosis of LS: Toward a
Consensus
MSI alone should not be used as a sole basis for
selecting patients for mutational testing for LS given
the modest but real fraction of patients with MSInegative tumors in which mutations were found.
**Lynch et al. J Natl Cancer Inst 99:261-263, 2007.
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BRAF V600E mutation and LS
BRAF V600E mutation can sort this out
since when detected it excludes LS and
contributes to improved costeffectiveness of genetic testing for LS.
*Clin Gastroenterol Hepatol 6:206-214, 2008.
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Clinical Relevance of MMR Deficiency*
Methods to identify MMR-deficient CRC in LS:
1) MSI;
2) IHC;
3) MLH1 promoter hypermethylation testing;
4) germline mutation analysis.
*Pal et al. Cancer 113:733-742, 2008.
MORPHOLOGY
SUSPICIOUS
FOR MSI-H
Run PCR test
for MSI status
Is there
MSI-H?
NO
NO
YES
Is there loss
of staining
with any of
the Abs?
Run mutation analysis
for BRAF V600E
Is there
BRAF V600E
mutation?
NO EVIDENCE OF
LYNCH
SYNDROME
NO
IHC for MLH1,
MSH2, MSH6, PMS2
YES
PUTATIVE
LYNCH
SYNDROME
MMR GENES MUTATION
ANALYSIS
YES
SPORADIC CRC
WITH MSI-H
NO
Is there
a mutation in MMR
gene?
YES
Gatalica Z, Torlakovic E. Fam Cancer 2008;7:15-26
LYNCH
SYNDROME
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Lynch syndrome (LS) and
Mismatch Repair (MMR) Genes:
What Are the Risks?
A new era for genetic counseling evolved thanks to
the cloning of MSH2, MLH1 and MSH6.
Prior to MMR mutation discovery we had to rely
solely on an individual’s family history.
Now we can determine lifetime risks for CRC and
extra colonic cancers by MMR testing.
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Do Molecular Genetic Changes
in CRC Impact Treatment?
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Early Evidence of 5-FU Resistence in Lynch
Syndrome
Carethers et al.* developed paradigms showing
MMR proficiency and the in vitro response to 5-FU.
*J Clin Invest 98:199-206, 1996.
Gastroenterology 117:123-131, 1999.
Gastroenterology 126:394-401, 2004.
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Efficacy of 5-FU Adjuvant Chemotherapy
and MMR Status
These investigators* studied the survival influence of 5FU in patients with MSI-H tumors.
Results:
Their findings showed that there is improved survival in
patients with non-MSI-H tumors after 5-FU-based
chemotherapy that does not extend to patients with
MSI-H. The MSI status of a patient’s CRC may indicate
differences in 5-FU-based chemotherapy.
These findings are consistent with in vitro studies
*Carethers et al. Gastroenterology 126:394-401, 2004.
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Efficacy of 5-FU Adjuvant Chemotherapy
and MMR Status
Ribic et al.* investigated 5-FU-based
chemotherapy which benefited patients with stage
II and stage III CRC.
They note that CRCs with MSI-H have clinical and
pathologic features that distinguish them from
MSS tumors. They investigated the usefulness of
MSI status as a predictor of the benefit of adjuvant
chemotherapy with 5-FU in stage II and stage III
CRC.
*N Engl J Med 349:247-257, 2003.
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Efficacy of 5-FU Adjuvant Chemotherapy
and MMR Status
Their study* showed that of 570 tissue specimens,
95 (16.7%) showed MSI-H.
Among 287 patients who did not receive adjuvant
chemotherapy, those with MSI-H tumors had a better
5-year rate of overall survival than patients with MSS
or MSI-L tumors (hazard ratio for death, 0.31, 95%
CI: 0.14-0.72; p = 0.04).
*Ribic et al. N Engl J Med 349:247-257, 2003.
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K-Ras Mutation in CRC*
Recent clinical data showed that the efficacy of
cetuximab and panitumumab is confined to
patients whose tumors have K-ras wild-type.
Conclusion:
K-ras mutation analysis considered a new
standard of care in the selection of patients for
epidermal growth factor receptor (EFGR)-targeted
therapy.
*Ramos & Caturla. Cancer & Chemotherapy
Reviews 3:194-203, 2008.
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MSI Status as a Predictor of Benefit from
5-FU-based Adjuvant Chemotherapy in CRC
Conclusion:
5-FU-based adjuvant chemotherapy benefitted
patients with stage II or III CRC with microsatellite
stable (MSS) tumors, tumors with low MSI
frequency (MSI-L), but not MSI-H tumors.
*N Engl J Med 349:247-257, 2003.
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Genetic Testing and Cancer Control
in Lynch Syndrome
The Evaluation of Genomic Applications in Practice
and Prevention (EGAPP) Working Group* constructed
a chain of evidence linking genetic testing for LS in
patients with newly dx CRC with improved health
outcomes in their relatives.
Does it work?
*Genet Med 11:35-41, 2009.
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Evaluation of Genomic Applications in Practice and
Prevention (EGAPP) of Lynch Syndrome*
Testing of all individuals with newly diagnosed
CRC proposed as a strategy to reduce CRC
morbidity and mortality in relatives of Lynch
syndrome (LS) affected.
Assessing patients who have newly Dx CRC with
a series of genetic tests (MSI, IHC, MMR) could
lead to the identification of LS. Relatives of
patients with LS could then be offered genetic
testing.
*Genetics in Medicine 11:35-41, 2009.
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Genetic Testing and Cancer Control
in Lynch Syndrome*
Testing of newly dx (with CRC) proband with a series
of genetic tests could lead to the identification of LS.
Relatives of proband with LS could then be offered
genetic testing and where indicated CRC and
endometrial cancer (EC) surveillance with expectation
of improved health outcome.
*EGAPP Working Group. Genet Med 11:35-41, 2009.
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Genetic Testing and Cancer Control
in Lynch Syndrome
Clinical Validity:
Accounting for specific technologies and numbers of
markers used, the EWG identified adequate evidence to
describe the clinical sensitivity and specificity of selected
testing strategies:
Most cost effective approach for LS screening is MSI
testing for all CRC, followed by MMR (MSH2 and MLH1)
testing when CRC is found to be MSI-H.
*EGAPP Working Group. Genet Med 11:35-41, 2009.
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Genetic Testing and Cancer Control
in Lynch Syndrome*
Screening for MSI is cost effective for patients with
newly dx CRC, because mutation identification in
MSI-H cases offers an opportunity to provide
predictive testing for at-risk relatives. .
Such testing enables targeted management for
mutation carriers, with population level screening
measures for non-carriers.
*EGAPP Working Group. Genet Med 11:35-41, 2009.
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Evaluation of Genomic Applications in Practice and
Prevention (EGAPP) of Lynch Syndrome*
Conclusion:
E W G concluded that there was moderate
certainty that such a testing strategy would
provide moderate population benefit.
*Genetics in Medicine 11:35-41, 2009.
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Biochemical Basis of MSI*
Boland et al. state that the dx of LS is becoming
more complex as more and more is learned about
the disease; one, therefore, needs to understand
how the DNA MMR proteins function and what
makes them malfunction to arrive at an optimal
appreciation of how to interpret diagnostic studies
such as MSI and IHC of the DNA MMR proteins.
*Boland et al. Fam Cancer 7:41-52, 2008.
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Biochemical Basis of MSI*
Conclusion:
Understanding the role of DNA MMR system in
regulation of the cell cycle and the response to
DNA damage helps illuminate the differences in
natural history and response to chemotherapeutic
agents seen in LS.
*Boland et al. Fam Cancer 7:41-52, 2008.
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Family Information Service (FIS)
Cost-effective and highly efficient way of
educating and counseling all available family
members from a geographic catchment area
during a single setting.
Makes best use of physician’s time and effort,
has group therapy potential and patients
welcome it.
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