Lynch Syndrome

Angie Strang, PGY2

Background

• Previously “hereditary nonpolyposis colorectal cancer”

• Autosomal dominant inherited cancer susceptibility syndrome

• Caused by defects in the mismatch repair system

• Types of cancer involved

– Colorectal Cancer

– Endometrial Cancer

– Ovarian Cancer

• Other cancers could include:

– Gastric, small bowel, hepatobiliary, renal pelvis, ureter, certain breast cancers, certain brain tumors, sebaceous skin tumors

Background

• Accounts for most cases of hereditary uterine and colorectal cancers

• Second most common cause of inherited ovarian cancer– Most common cause is hereditary breast and ovarian cancer

syndrome

• Prevalence = 1:600-3000

• Lynch syndrome results in more early-onset endometrial and colorectal cancers

• In women < 50 yrs old, increased finding of deleterious mismatch repair gene mutation associated with cancer:– Found in 5-9% of women with endometrial cancer

– Found in 5-7% of women with colorectal cancer

Background

• According to a retrospective review of women with GI and gyn metachronous (separate malignancies arising at different times):

– When endometrial cancer was the presenting diagnosis, there was a median of 11 yrs before the diagnosis of colon cancer

Cancer Risks

• Colorectal cancer

– Risk in general population, women though age 70 = 1.7%

– Risk in Lynch syndrome, women though age 70 = 18-61%

• Endometrial cancer

– Risk in Lynch syndrome, women though age 70 = 16-61%

• Ovarian cancer

– Risk in general population, women though age 70 = ~1%

– Risk in Lynch syndrome, women though age 70 = 5-10%• Patients with BRCA1, risk = 39-46%

• Patients with BRCA2, risk = 12-20%

Genetics

• Involves: MLH1, MSH2, MSH6, PMS2

• Deletions in the EpCAM gene also may lead to inactivation of MSH2, leading to Lynch Syndrome

• Endometrial cancer risk

– MLH1 mutation carriers = 20-54% risk by age 70

– MSH2 mutation carriers = 21-49% risk by age 70

– MSH6 mutation carriers = 16-61% risk by age 70

• Later age of onset

Pathogenesis

• Defects in mismatch repair genes leads to genomic instability

– Instability occurs in the entire genome and includes noncoding single nucleotide and dinucleotide repeats (microsatellites) throughout the DNA

• Microsatellite instability can also result from noninherited methylation of the MLH1 promoter

– Seen in 20-30% of cases of endometrial cancer

– Seen in 15-20% of cases of colon cancer

Risk Assessment:The Bethesda Guidelines

Patients who should be considered for further eval of Lynch syndrome:

• Endometrial or colorectal cancer diagnosed < age 50• Endometrial or ovarian cancer with a synchronous or

metachronous colon or other Lynch/HNPCC-associated tumor at any age

• Colorectal cancer with tumor-infiltrating lymphocytes, peritumoral lymphocytes, Crohn-like lymphocytic reaction, mucinous/signet-ring differentiation, or medullary growth pattern diagnosed < age 60

• Endometrial or colorectal cancer and a 1st degree relative with a Lynch/HNPCC-associated tumor diagnosed < age 50

• Colorectal or endometrial cancer diagnosed at any age with 2+ 1st or 2nd degree relatives with Lynch/HNPCC-associated tumors, regardless of age

Testing for Lynch Syndrome

1. Direct germline DNA testing

– sequencing and screening for large rearrangements in of the relevant mismatch repair genes

– *Absence of a deleterious mutation does not exclude Lynch syndrome, so usually testing is done first with tumor immunohistochemistry

Testing for Lynch Syndrome

2. Tumor testing with immunohistochemistry or microsatellite instability testing

– Inexpensive and available at most path labs

– Allows for identification of which mismatch repair proteins are missing and can guide subsequent germline DNA testing

– If all 4 mismatch repair proteins are present, it does NOT r/oLynch syndrome, and it means that a deleterious mutation is allowing the production of a full-length, but nonfunctional protein

– If you have high clinical suspicion of Lynch syndrome and normal immunohistochemistry results, then you can further evaluate with microsatellite instability testing

*Start here if possible!

Testing for Lynch Syndrome

3. Microsatellite Instability Testing

– You need normal tissue and tumor tissue from the patient with a potential Lynch syndrome-associated tumor

– They compare the normal and abnormal tissues and determine if there has been an insertion or deletion of nucleotides to informative microsatellites

– If NO microsatellite instability is detected, it essentially rules out the presence of Lynch syndrome

Testing for Lynch Syndrome

4. MLH1 Promoter Methylation Testing

– Need to do this if the immunohistochemical testing reveals absence of the MLH1 protein (with or w/out absence of the PMS2 protein) or when microsatellite instability is present

– If MLH1 protein absent + methylation of MLH1 promoter = NOT Lynch syndrome

– If MLH1 protein absent + NO methylation of MLH1 promoter = patient needs germline DNA testing for Lynch syndrome

Recap: Testing for Lynch Syndrome

Recommendations

• If your patient has colorectal or endometrial cancer, you should use one of these approaches to assess for the possibility of Lynch Syndrome:

1. Tumor testing on any endometrial or colorectal tumor from a woman who is at risk for Lynch syndrome (thorough H&P). Use Bethesda Guidelines to determine at risk patients.

2. Tumor testing on all endometrial or colorectal tumors irrespective of age of diagnosis

3. Tumor testing on all endometrial or colorectal tumors before age 60

*Level B evidence

Recommendations

• Which patients without cancer should be offered hereditary cancer risk assessment for Lynch syndrome?

– If they have a 1st degree relative w/ endometrial or colorectal cancer who was either diagnosed before age 60, or who is identified to be at risk for Lynch syndrome by one of the systematic clinical screens that incorporates a focused personal and family medical history

*Level B evidence

Recommendations

• If the patient has a personal or family hx of Lynch syndrome-associated cancer and tumor tissue IS available– test the patient’s specimen

– If patient unaffected: make every effort to obtain a tissue block from the specimen from the affected relative

*Level B Evidence (tumor testing when possible)

• If the patient has a personal or family hx of Lynch syndrome-associated cancer and tumor tissue IS NOT available– Germline DNA testing may be considered after counseling

– In this setting the finding of a deleterious germline DNA mutation would confirm Lynch syndrome

– Absence of germline DNA mutation does not exclude the syndrome

Recommendations

• If tumor testing is suspicious for Lynch syndrome, but germline DNA tests are normal:

– consultation w/ genetics professional

– *Germline testing may not identify a causative mutation in up to 40% of cases

Risk Reduction forWomen with Lynch Syndrome

• Screening– Colonoscopy every 1-2 yrs starting at age 20-25, OR

2-5 yrs before the earliest cancer dx in the family,(whichever is earliest)

– Endometrial biopsy every 1-2 yrs starting at age 30-35– Keeping a menstrual calendar and evaluation of abnormal

uterine bleeding*Level B Evidence

• No consensus on ovarian cancer surveillance in women with Lynch syndrome– In the largest gyn cancer surveillance study to date, neither

sono nor CA-125 testing led to the diagnosis of ovarian cancer in any of the 175 Lynch syndrome mutation carriers who were screened

Risk Reduction forWomen with Lynch Syndrome

• Chemoprevention for endometrial cancer

– OCPs can reduce risk in general population by 50%

– Progestin therapy is effective for tx of endometrial hyperplasia and early endometrial cancer

*Level C Evidence (progestin-based contraception)

Risk Reduction forWomen with Lynch Syndrome

Risk-Reducing Surgery (Level B Evidence)• Prophylactic hyst + BSO

• By mid-40s, should discuss surgery w/ pt– By age 40, risk of:

• Endometrial cancer = 2-4%

• Ovarian cancer = 1-2%

– By age 50, risk of:• Endometrial cancer = 8-17%

• Ovarian cancer = 3-7%

• Surgery should be via vaginal or minimally-invasive approach

• If pt wants to keep her ovaries – still remove the tubes

• Consider doing surgery in conjunction with colorectal surgery if applicable, so make sure their colonoscopy is up to date

References

• ACOG Practice Bulletin #147, November 2014: Lynch Syndrome

• Genetics Home Reference: Lynch Syndromehttp://ghr.nlm.nih.gov/condition/lynch-syndrome