Genetic testing all you need to know Sue Clark Consultant Colorectal Surgeon, St Mark s Hospital, London, UK.
Colorectal cancer Familial 33% Polyposis syndromes <1% Lynch syn 4% Sporadic 64% Lichtenstein et al. N Engl J Med 2000
Colorectal cancer high risk group Lynch syndrome Familial adenomatous polyposis MUTYH associated polyposis Gene Frequency Cumulative lifetime risk of CRCa MMR (MLH1, MSH2 etc) EPCAM ~1:500 50-70% APC 1:10 000 ~100% MUTYH (recessive) ~1:30 000 50-90% Juvenile polyposis SMAD4 / BMPR1A 1:100 000 ~25-50% Peutz Jeghers syndrome STK11 ~1:100 000 ~15-40% PTEN hamartoma tumour syndrome (Cowden / BRR) Polymerase proofreading associated polyposis Hereditary mixed polyposis syndrome Serrated polyposis syndrome PTEN ~1:200 000 10-15% POLD1 / POLE?? GREM1??? 1:3 000?
Why do genetic testing at all? Treatment of cancer in a patient with a high risk syndrome altered surgical approach extended colectomy / proctocolectomy consider prophylactic TAH & BSO different indications for adjuvant therapy Individual patient surveillance +/- prophylactic surgery improves life expectancy aspirin pre-implantation genetic diagnosis At-risk family members predictive genetic testing
How do you do it? Genetic counselling and consent Take a sample blood saliva/buccal scrape skin biopsy bowel biopsy DNA extraction and sequencing
Next generation sequencing
Variant interpretation Pitfalls Mosaicism bone marrow transplant Phenocopies Complex families non-paternity adoption etc, etc
Who should we test? EVERYONE NOBODY SELECTED GROUP
Colorectal cancer high risk group Lynch syndrome Familial adenomatous polyposis MUTYH associated polyposis Gene Frequency Cumulative lifetime risk of CRCa MMR (MLH1, MSH2 etc) EPCAM ~1:500 50-70% APC 1:10 000 ~100% MUTYH (recessive) ~1:30 000 50-90% Juvenile polyposis SMAD4 / BMPR1A 1:100 000 ~25-50% Peutz Jeghers syndrome STK11 ~1:100 000 ~15-40% PTEN hamartoma tumour syndrome (Cowden / BRR) Polymerase proofreading associated polyposis Hereditary mixed polyposis syndrome Serrated polyposis syndrome PTEN ~1:200 000 10-15% POLD1 / POLE?? GREM1??? 1:3 000?
Polyposis syndromes Diagnosis colonoscopy / pathology histology number (>10 adenomas) extra-colonic manifestations family history genetic testing
Colorectal cancer high risk group Lynch syndrome Familial adenomatous polyposis MUTYH associated polyposis Gene Frequency Cumulative lifetime risk of CRCa MMR (MLH1, MSH2 etc) EPCAM ~1:500 50-70% APC 1:10 000 ~100% MUTYH (recessive) ~1:30 000 50-90% Juvenile polyposis SMAD4 / BMPR1A 1:100 000 ~25-50% Peutz Jeghers syndrome STK11 ~1:100 000 ~15-40% PTEN hamartoma tumour syndrome (Cowden / BRR) Polymerase proofreading associated polyposis Hereditary mixed polyposis syndrome Serrated polyposis syndrome PTEN ~1:200 000 10-15% POLD1 / POLE?? GREM1??? 1:3 000?
Who should have genetic testing for Lynch syndrome? Individuals with colorectal (or other Lynch syndrome related) cancer and Family history Amsterdam II criteria or Tumour characteristics of mismatch repair defect MMR immunohistochemistry / MSI MLH1 promoter methylation / BRAF
60% sporadic + FAP APC small adenoma KRAS large adenoma SMAD4 P53 cancer - Jass 4 CI MSS CIMP negative slow development M>F, L>R budding normal bowel 15% sporadic MLH1 promoter methylation serrated polyp BRAF cancer - Jass 1 CS MSI CIMP high F>M, R>L no budding, lymph+ poor prognosis? MMR mutation Lynch syndrome accelerated adenoma development flat adenoma cancer -? CS MSS CIMP negative poor prognosis TGFß (KRAS) cancer - Jass 5 CS MSI CIMP negative fast development M>F, R>L little budding, lymph+ good prognosis
Guinney et al. Nature Med 2015
Mismatch repair immunohistochemistry
Microsatellite instability (MSI) Papa likes bananas Papa likes banananas Papapa likes bananas Papapapa likes banananas Papa likes banananananas Papapapa likes bananananananas etc
Microsatellite instability (MSI) Heterozygote N Tumour CACACACACA CACACACACACACA
60% sporadic + FAP APC small adenoma KRAS large adenoma SMAD4 P53 cancer - Jass 4 CI MSS CIMP negative slow development M>F, L>R budding normal bowel 15% sporadic MLH1 promoter methylation serrated polyp BRAF cancer - Jass 1 CS MSI CIMP high F>M, R>L no budding, lymph+ poor prognosis? MMR mutation Lynch syndrome accelerated adenoma development flat adenoma cancer -? CS MSS CIMP negative poor prognosis TGFß (KRAS) cancer - Jass 5 CS MSI CIMP negative fast development M>F, R>L little budding, lymph+ good prognosis
Which tumours should be tested and how?
Which tumours? none Amsterdam II criteria Bethesda criteria all under 60y all under 70y all How? MMR-IHC MSI both BRAF MLH1 promoter methylation go straight to genetic testing
CRCa <70y, all synchronous/metachronous LS Ca, Amsterdam +ve MMR- IHC Normal Not Lynch syndrome Loss of MLH1/PMS2 Loss of MSH2/MSH6 Methylation MLH1 promoter methylation testing No methylation Genetic testing Lynch syndrome
Summary Confusing and fast moving area evolving technology various confusing criteria too many options Should get simpler as genetic testing becomes more universal 100k genome project etc Get to know your genetics team develop and refine pathways together
St Mark s Hospital & Academic Institute Lecture Course Frontiers in Intestinal and Colorectal Disease 22 nd 25 th November 2016 www.stmarksacademicinstitute.org.uk Email: info@stmarksacademicinstitute.org.uk St Mark s Academic Institute, St Mark s Hospital, Northwick Park Harrow, Middlesex HA1 3UJ Sir Alan Parks Visiting Professor Professor Michael Solomon, Sydney, Australia Sir Francis Avery Jones Visiting Professor Professor Evelien Dekker, Amsterdam, Netherlands