What is the recommended evaluation, genetic testing, and management for an individual suspected of having a hereditary colorectal cancer syndrome?

Hereditary Colorectal Cancer Syndromes: Evaluation, Genetic Testing, and Management

Initial Risk Stratification and Referral

All patients with suspected hereditary colorectal cancer should undergo tumor-based MMR/MSI testing as the first diagnostic step, followed by syndrome-specific genetic testing when indicated. 1

Minimum Threshold for Specialist Referral

• Moderate familial CRC risk (defined as a family history meeting specific criteria) is the minimum threshold for referral from primary care to a specialist familial CRC clinic 1
• Patients with deficient MMR (without MLH1 promoter methylation or BRAF V600E mutation) or polyposis require referral to a specialist service with access to constitutional genetic testing 1
• High-risk families are defined as ≥3 first-degree relatives with CRC across >1 generation 1

Universal Tumor Testing Strategy

All Colorectal Cancers

• Universal tumor testing with immunohistochemistry for MMR proteins (MLH1, MSH2, MSH6, PMS2) and/or MSI testing should be performed on all newly diagnosed CRC patients 1, 2
• This serves dual purposes: (1) identifies MSI-high/dMMR tumors eligible for immunotherapy rather than standard chemoradiotherapy, and (2) detects hereditary Lynch syndrome 2

Reflex Testing Algorithm

• If MLH1/PMS2 loss is detected: perform BRAF V600E mutation analysis or MLH1 promoter methylation testing to exclude sporadic cases 1
• If loss of MSH2, MSH6, or PMS2 is observed: proceed directly to germline genetic testing for the corresponding genes 1
• If MLH1 loss without methylation/BRAF mutation: proceed to germline testing 1

Syndrome-Specific Genetic Testing Protocols

Lynch Syndrome (HNPCC)

Testing Indications:

• Early-onset CRC: All patients diagnosed with CRC at ≤30 years require constitutional panel testing determined by MMR status 1
• Family history: MMR status should be assessed in tumor tissue from a close affected family member for all patients referred with family history of CRC 1
• Amsterdam criteria families where MMR testing is not possible may receive panel testing of affected individuals 1

Comprehensive Testing Requirements:

• Full germline genetic testing must include both DNA sequencing and large rearrangement analysis of MMR genes 1

Polyposis Syndromes

Familial Adenomatous Polyposis (FAP):

• Patients with ≥10 adenomas should be considered for germline APC testing 1
• Full germline APC testing must include DNA sequencing and large rearrangement analysis 1
• Reported family history of polyposis must be verified by review of histopathology/endoscopy reports confirming ≥10 adenomas or serrated lesions in a first-degree relative 1

MUTYH-Associated Polyposis (MAP):

• Testing can be initiated by screening for the most common mutations (G396D, Y179C) in white populations, followed by full gene analysis in heterozygotes 1
• For non-white individuals, full MUTYH sequencing should be performed initially 1
• Indicated for patients <60 years with ≥10 adenomas, or >60 years with ≥20 adenomas, or ≥10 with family history of multiple adenomas or CRC 1

Other Polyposis Syndromes:

• Peutz-Jeghers syndrome: STK11 gene testing 1
• Juvenile polyposis syndrome: SMAD4 and BMPR1A gene testing 1

Lynch-Like Syndrome

• For dMMR tumors without hypermethylation/BRAF pathogenic variant and no constitutional MMR pathogenic variant, perform somatic testing panel on tumor tissue 1
• If two somatic MMR pathogenic variants are identified, manage patient and first-degree relatives according to family-history-driven CRC criteria 2
• If zero or one somatic variant is found, manage patient and first-degree relatives using standard Lynch syndrome protocols 2

Multiple Colorectal Adenomas (MCRAs)

• Constitutional gene panel testing is indicated for MCRAs <60 years with ≥10 adenomas, or >60 years with ≥20 adenomas, or ≥10 with family history 1

Surveillance Protocols by Syndrome

Lynch Syndrome

Colonoscopy:

• MLH1 and MSH2 carriers: Start at age 25 years, every 2 years until age 75 1
• MSH6 and PMS2 carriers: Start at age 35 years, every 2 years until age 75 1

Gynecological Surveillance:

• Annual gynecological examination with transvaginal ultrasound and endometrial aspiration biopsy starting at age 30-35 years 1, 3
• Prophylactic hysterectomy and bilateral salpingo-oophorectomy should be discussed after childbearing completion, typically age 35-40 years 1, 3
• MLH1 carriers: Consider surgery at age 40 years due to higher early-onset risk 3

Other Surveillance:

• Gastric, small bowel, and pancreatic screening should be limited to clinical trial settings 2
• Screen for Helicobacter pylori infection and provide eradication therapy when positive 3

Familial Adenomatous Polyposis (FAP)

Colorectal:

• APC pathogenic variant carriers: Colonoscopy starting age 12-14 years, every 1-3 years depending on phenotype 1
• At-risk individuals without identified variant: Colonoscopy starting age 12-14 years, every 5 years until national screening age 1
• Sigmoidoscopy/pouchoscopy from time of colectomy, every 1-3 years depending on phenotype 1

Upper GI:

• Gastroscopy and duodenoscopy starting age 25 years, interval determined by Spigelman classification 1

MUTYH-Associated Polyposis (MAP)

• Colonoscopy: Starting age 18-20 years, annually 1
• Gastroscopy and duodenoscopy: Starting age 35 years, interval per Spigelman classification 1

Peutz-Jeghers Syndrome (PJS)

• Upper GI endoscopy, colonoscopy, and video capsule endoscopy: Starting age 8 years 1

Juvenile Polyposis Syndrome (JPS)

Colonoscopy:

• SMAD4 and BMPR1A carriers: Starting age 15 years, every 1-3 years depending on phenotype 1

Upper GI:

• SMAD4 carriers: Gastroscopy and duodenoscopy starting age 18 years, every 1-3 years 1
• BMPR1A carriers: Gastroscopy and duodenoscopy starting age 25 years, every 1-3 years 1

Family History Only (No Identified Syndrome)

Moderate Risk:

• One-off colonoscopy at age 55 years 1
• Subsequent surveillance per post-polypectomy guidelines 1

High Risk (≥3 FDRs with CRC across >1 generation):

• Colonoscopy every 5 years from age 40 to 75 years 1

Lynch-Like Syndrome

• Colonoscopy starting age 25 years, every 2 years until age 75 for affected individuals and their unaffected first-degree relatives 1

Serrated Polyposis Syndrome

• Affected individuals: Colonoscopy from age of diagnosis, every 1-2 years until age 75 1
• First-degree relatives: Colonoscopy starting age 40 (or 10 years earlier than index case), every 5 years until age 75 1

Multiple Colorectal Adenomas (≥10 without APC/MUTYH variants)

• Colonoscopy from age of diagnosis, every 1-2 years until age 75 1

Chemoprevention and Lifestyle Modification

Lynch Syndrome

• Daily aspirin is strongly recommended to reduce CRC risk (moderate evidence, strong recommendation) 1, 3
• Patients should be offered research opportunities for different aspirin dosages; if they decline, counsel on dose choices, risks/benefits, and ensure their medical practitioner is aware 1

General Recommendations

• Strongly encourage: smoking cessation, maintain normal BMI, moderate consumption of red and processed meat, regular exercise 1
• There is insufficient evidence for chemoprophylaxis benefit in polyposis syndromes 1

Surgical Management Considerations

Lynch Syndrome with Rectal Cancer

• Standard low anterior resection is acceptable when abdominoperineal excision can be avoided, despite high metachronous neoplasia risk 2
• MSH6 or PMS2 carriers: Insufficient evidence to support extended colectomy over segmental resection 2
• MLH1 or MSH2 carriers: Balance metachronous cancer risk, functional outcomes, patient age, and preferences when choosing between segmental versus extended colectomy 2

FAP

• Surgery is indicated when there are large numbers of adenomas including those with high-grade dysplasia 1
• Choice between total colectomy with ileorectal anastomosis (IRA) versus proctocolectomy with ileal pouch-anal anastomosis (IPAA) depends on: patient age, severity of rectal polyposis, childbearing wishes, desmoid risk, and possibly APC mutation site 1

Attenuated FAP

• Some patients can be conservatively managed with colonoscopy every 1-2 years and polypectomy 1

Critical Pitfalls to Avoid

• Do not omit universal tumor testing: Missing an MSI-high result can change treatment from chemoradiotherapy to immunotherapy 2
• Do not assume negative germline testing excludes hereditary syndrome when family history is strongly suggestive; apply the same surveillance as for confirmed carriers 1
• Do not overlook extracolonic surveillance: Endometrial and urinary tract cancers are part of the Lynch syndrome spectrum 2
• Do not delay genetic counseling due to reproductive concerns: The two issues are independent but reproductive context heightens testing urgency 3
• Do not recommend prophylactic surgery based solely on family history without genetic testing, as this represents overtreatment for most patients 3

Service Delivery Requirements

• Hospitals managing hereditary CRC patients must ensure clinical pathways to facilitate care and processes to monitor service quality 1
• Patients should receive specialist knowledge and be made aware of patient/support organizations, lifestyle discussions, and research participation opportunities 1
• Approximately 95% of relatives who receive genetic counseling proceed with genetic testing 3