Guidelines on genetic evaluation and management of Lynch syndrome: a consensus statement by the US Multi-Society Task Force on colorectal cancer

The Multi-Society Task Force, in collaboration with invited experts, developed guidelines to assist health care providers with the appropriate provision of genetic testing and management of patients at risk for and affected with Lynch syndrome as follows: Figure 1 provides a colorectal cancer risk assessment tool to screen individuals in the office or endoscopy setting; Figure 2 illustrates a strategy for universal screening for Lynch syndrome by tumor testing of patients diagnosed with colorectal cancer; Figures 3-6 provide algorithms for genetic evaluation of affected and at-risk family members of pedigrees with Lynch syndrome; Table 10 provides guidelines for screening at-risk and affected persons with Lynch syndrome; and Table 12 lists the guidelines for the management of patients with Lynch syndrome. A detailed explanation of Lynch syndrome and the methodology utilized to derive these guidelines, as well as an explanation of, and supporting literature for, these guidelines are provided.

Guidelines on genetic evaluation and management of Lynch syndrome: a consensus statement by the US Multi-society Task Force on colorectal cancer

The Multi-Society Task Force, in collaboration with invited experts, developed guidelines to assist health care providers with the appropriate provision of genetic testing and management of patients at risk for and affected with Lynch syndrome as follows: Figure 1 provides a colorectal cancer risk assessment tool to screen individuals in the office or endoscopy setting; Figure 2 illustrates a strategy for universal screening for Lynch syndrome by tumor testing of patients diagnosed with colorectal cancer; Figures 3,4,5,6 provide algorithms for genetic evaluation of affected and at-risk family members of pedigrees with Lynch syndrome; Table 10 provides guidelines for screening at-risk and affected persons with Lynch syndrome; and Table 12 lists the guidelines for the management of patients with Lynch syndrome. A detailed explanation of Lynch syndrome and the methodology utilized to derive these guidelines, as well as an explanation of, and supporting literature for, these guidelines are provided.

Rectal cancers in patients with familial adenomatous polyposis

Patients with familial adenomatous polyposis may develop rectal cancer at their initial presentation (primary) or after colectomy and ileorectal anastomosis (secondary). Little is known about whether differences in presentation impact survival. We hypothesize that patients with secondary rectal cancer have better oncologic outcomes. Patients with rectal cancer in the context of familial adenomatous polyposis were classified into 3 groups: known rectal cancer at presentation, incidental rectal cancer unrecognized before proctocolectomy, and rectal cancer diagnosed after ileorectal anastomosis. Primary endpoint was 5-year survival. There were 58 patients, 39 with primary rectal cancer, 5 of which were incidental, and 19 with secondary rectal cancer. Median ages at diagnosis were 32 years (range 14-56) for primary cancer, 35 years (range 22-56) for incidental cancer and 49 years (range 24-66) for secondary cancer (p = 0.001). 76% of those with primary rectal cancer had symptoms, similar to those with incidental cancer (60%) but more than secondary cancer (21%) (p < 0.001). 47% of primary cancers were advanced (stages III and IV) compared to 20% of incidental cancers and 32% of secondary cancers. There was no local recurrence in any patient, but 9 patients had distant recurrences (16% overall). Overall 5-year survival of patients with primary cancer was 72.4%, incidental cancer was 100%, and secondary cancer was 69.7% (p = 0.031). More patients with primary rectal cancer have advanced disease but survival is similar to those with cancer diagnosed on surveillance. More patients with primary rectal cancer have a restorative resection when compared to other groups.

Risk factors for delayed postpolypectomy bleeding: how to minimize your patients' risk

PURPOSE

Secondary bleeding after colonoscopic polypectomy is a serious complication. Most studies show polyp size, location, and shape to be important risk factors but other factors may allow refinement of risk. The aim of this study is to look for other factors associated with delayed postpolypectomy bleeding.

METHODS

This case-matched study compares patients who developed postpolypectomy bleeding with those who underwent uncomplicated polypectomy. Matching was performed for known risk factors: polyp size, location and shape, with a ratio of three controls to one subject.

RESULTS

Postpolypectomy bleeding occurred in 19/494 patients with polyps >2.0 cm diameter (3.8%) and 11/4161 patients with polyps <2.0 cm (0.3%). There was a median interval of 3 days (range 0-9 days) from polypectomy to hemorrhage. Twenty-five patients were readmitted to this institution. Ten (40.0%) were transfused and 19 (76.0%) were re-colonoscoped, with 13 needing either cautery (n = 7) or adrenaline injection (n = 6). Ninety patients were selected as controls, matched for polyp size, location, and shape. Mean age at polypectomy was 69.9 ± 9.2 years for patients and 64.9 ± 12.2 for controls (p = 0.042); 63.3% subjects were male, compared to 47.8% of controls (p = 0.140). Univariate analysis showed that older age, piecemeal polypectomy, need for additional sedation, concurrent diverticulosis and intraprocedural bleeding were significantly associated with increased risk of delayed bleeding. The associations between delayed bleeding and additional sedation, concurrent diverticulosis and intraprocedural bleeding were confirmed by multivariate logistic regression analysis.

CONCLUSION

Difficult colonoscopy and intraprocedural bleeding identify patients with a particularly high risk of secondary postpolypectomy bleeding. Preventive measures should be considered in such cases.

Should bypass or stoma creation be undertaken for unresectable stage IV colorectal carcinoma?

BACKGROUND

When patients with stage IV colorectal cancer are deemed to have an unresectable primary colorectal cancer or extensive metastases at surgery, bypass or stoma creation may be the only surgical options. Whether this surgical approach provides extra months of life or instead leads to prohibitive post-operative morbidity and mortality has not previously been well characterized. This study was conducted to evaluate early and long-term outcomes for stage IV colorectal cancer patients with unresectable primary tumour.

METHODS

Patients with unresectable colorectal cancer who underwent palliative bypass or stoma creation were identified from a prospective colorectal cancer database. Early and long-term outcomes were evaluated. Survival was determined using Kaplan-Meier survival curves.

RESULTS

From 1980 to 2008, 81 patients with stage IV colorectal cancer had an unresectable primary or extensive metastases and underwent palliative bypass or stoma creation. Mean age was 61.5 ± 13.9 years, 44 (54.3%) were male. Location of the colorectal cancer was left-sided in 82.7%. Of the patients, 38.3% had emergency or urgent surgery. Sixty-two (76.5%) patients underwent a diverting stoma, 15 (18.5%) underwent enteric bypass procedures and 4 (4.9%) had both a diverting stoma and proximal bypass created. Twenty-five complications occurred in 24 patients (29.6%) with 2 patients (2.5%) requiring further re-operation. There was no anastomotic leak. Mean length of hospital stay was 13.8 ± 11.2 days. Thirty-day mortality rate was 16%. The median overall survival was 4.7 months, while the overall survival at 1 year was 24.7%. At 2 years, 6.1% patients were alive, all with a stoma.

CONCLUSION

Palliative bypass or stoma creation is associated with survival for several months for a significant proportion of patients with stage IV colorectal cancers, who have unresectable primaries or extensive metastases. The findings of this study support the use of bypass or diversion when faced with an unresectable primary in patients with colorectal cancer with metastases.

Results from an American Society of Colon and Rectal Surgeons survey on the management of young-onset colorectal cancer

BACKGROUND

Young patients with colorectal cancer (CRC) present a diagnostic and clinical challenge. The aim of our study was to survey the approaches to preoperative evaluation and clinical management of young patients with CRC by colorectal surgeons in North America.

METHODS

A standard electronic survey was sent to the members of the American Society of Colon and Rectal Surgeons. The survey polled management decisions in various clinical scenarios for CRC patients less than 50 years old. Survey responses were collated and analyzed.

RESULTS

One hundred ninety surgeons responded and 140 completed the entire survey (response rate 10%). Eighty percent of surgeons would offer preoperative genetic testing if the patient's family met the Amsterdam criteria compared to only 67% if the criteria were not met. Of those offering preoperative tumor testing, 48% test microsatellite instability, 19% mismatch repair protein expression by immunohistochemistry, and 24% offer both. Decisions regarding the extent of the resection for cancer were dependent on family history: Most members (86%) would perform a segmental colectomy for CRC in a patient without family history. Eighty-four percent of respondents would offer a total abdominal colectomy if preoperative tests indicated Lynch syndrome. When questioned about MYH-associated polyposis, only 27% recognized the appropriate diagnosis.

CONCLUSIONS

Among the American Society of Colon and Rectal Surgeons, family history influences preoperative testing and surgical management decisions. A significant portion of surgeons do not offer preoperative genetic testing, despite implications on operative management, postoperative surveillance, and screening of family members.

Integrated analysis of genome-wide copy number alterations and gene expression in microsatellite stable, CpG island methylator phenotype-negative colon cancer

Microsatellite stable (MSS), CpG island methylator phenotype (CIMP)-negative colorectal tumors, the most prevalent molecular subtype of colorectal cancer, are associated with extensive copy number alteration (CNA) events and aneuploidy. We report on the identification of characteristic recurrent CNA (with frequency >25%) events and associated gene expression profiles for a total of 40 paired tumor and adjacent normal colon tissues using genome-wide microarrays. We observed recurrent CNAs, namely gains at 1q, 7p, 7q, 8p12-11, 8q, 12p13, 13q, 20p, 20q, Xp, and Xq and losses at 1p36, 1p31, 1p21, 4p15-12, 4q12-35, 5q21-22, 6q26, 8p, 14q, 15q11-12, 17p, 18p, 18q, 21q21-22, and 22q. Within these genomic regions we identified 356 genes with significant differential expression (P < 0.0001 and ±1.5-fold change) in the tumor compared to adjacent normal tissue. Gene ontology and pathway analyses indicated that many of these genes were involved in functional mechanisms that regulate cell cycle, cell death, and metabolism. An amplicon present in >70% of the tumor samples at 20q11-20q13 contained several cancer-related genes (AHCY, POFUT1, RPN2, TH1L, and PRPF6) that were upregulated and demonstrated a significant linear correlation (P < 0.05) for gene dosage and gene expression. Copy number loss at 8p, a CNA associated with adenocarcinoma and poor prognosis, was observed in >50% of the tumor samples and demonstrated a significant linear correlation for gene dosage and gene expression for two potential tumor suppressor genes, MTUS1 (8p22) and PPP2CB (8p12). The results from our integration analysis illustrate the complex relationship between genomic alterations and gene expression in colon cancer.

Biological immunomodulators improve the healing rate in surgically treated perianal Crohn's fistulas

AIM

The role of biological therapy in perianal fistulas associated with Crohn's disease (CD) is uncertain as available data are confused and conflicting. In order to provide some clarity to the issue we have examined a large cohort of patients with perianal fistulas and CD and stratified them according to use of biological agents.

METHOD

Patients with perianal Crohn's fistulas treated between June 1999 and June 2009 were stratified according to use of biological agents and outcome was examined. Healing was defined as absence of fistula or drainage. Prior to surgery perianal sepsis was eradicated with drains or setons. Endpoints were defined as either complete healing, improvement (minimal symptoms and drainage) or unhealed, as noted at subsequent outpatient follow-up. Variables assessed were age, body mass index, smoking, perineal involvement with Crohn's granuloma and type of procedure. Fisher's exact test and χ(2) test were used for analysis.

RESULTS

Two hundred and eighteen patients had anal fistulas and CD. Mean follow-up was 3.2±3 years with mean age 38.8±12.2years and body mass index of 25.3±6. One hundred and seventeen patients (53.7%) underwent surgery alone (Group A) and 101 patients (46.3%) underwent surgery and biological immunomodulator treatments (Group B). Demographic data and CD history were similar between groups. Surgeries included seton drainge (n=90), fistulotomy (n=22), rectal advancement flap (n=39), fistulotomy plus seton (n=47) and others (n=20). Overall improvement in Group A was in 42 patients (35.9%) vs 72 patients (71.3%) in Group B (P=0.001). There was no significant difference in other studied variables between both groups.

CONCLUSIONS

There is a definite role for biological therapy as an adjuvant to surgery in patients with perianal fistulas and CD.

Interview: Polyposis research in colorectal cancer

James M Church speaks to Ruth Williamson, Commissioning Editor: JM Church’s career has been dedicated to saving and improving the lives of patients afflicted with intestinal disease. His main interests have been the prevention, detection and treatment of colorectal cancer, and in particular the hereditary forms of the disease. JM Church formed the Collaborative Group of the Americas in 1995 to help improve the care of patients and families with hereditary colorectal cancer in the USA, and in other countries of the Americas. He has served as Administrative Director ever since, and as president for one 2-year term. JM Church has also been chairman of the other international groups concerned with hereditary colorectal cancer: the Leeds Castle Polyposis Group and the International Collaborative Group on HNPCC. He is actively engaged in the clinical care, education and research of the syndromes of hereditary colorectal cancer.

High-throughput arrays identify distinct genetic profiles associated with lymph node involvement in rectal cancer

BACKGROUND

Preoperative clinical diagnosis of lymph node involvement guides treatment decisions for rectal cancer. Unfortunately, clinical staging still suffers from a lack of accuracy.

OBJECTIVE

The aim of this study was to evaluate objective genetic differences in primary rectal cancers with and without associated lymph node metastasis.

DESIGN

cDNA microarrays were generated from fresh-frozen tumors. Normalized data underwent global unsupervised hierarchical clustering analysis, and discriminating genes were mapped. Top discriminating genes were compared between stage II and III rectal cancers by use of an empirical Bayes 2 group t test with the Statistical Analysis of Microarrays and the Reproducibility-Optimized Test Statistic software separately to guide data reduction and deal with the difficulties of simultaneous statistical inference. Ingenuity Pathways Analysis software was used to analyze discriminating genes in terms of function and biological processes.

PATIENTS

Fifty-five patients with stage II and 22 patients with stage III rectal adenocarcinomas not treated with chemoradiation were included.

RESULTS

Two major unsupervised clusters emerged representing stage II and III cancers. In 1 cluster, 11 of 12 patients (92%) had stage III cancer; in the other cluster, 54 of 65 patients (83%) had stage II (p < 0.001). Five significantly differentially expressed genes characterized the stage III cluster: interleukin-8, 3-hydroxy-3-methylglutaryl coenzyme A synthase, carbonic anhydrase, ubiquitin, and cystatin (all p < 0.05). Of the 12 patients with differential expression of the 5 marker genes, only one had stage II cancer. Fifty-four of 55 stage II patients clustered with alternative expression patterns of the predictor genes. Differentially expressed genes are related to cancer-associated processes, pathways, and networks.

LIMITATIONS

The identified gene signatures have not yet been validated in independent patient populations.

CONCLUSIONS

Distinct gene expression signatures from primary rectal adenocarcinomas can help differentiate the presence or absence of lymph node metastases. These data are informative, and validation of this gene signature may provide a novel approach for more appropriate individualized treatment selection.

cis-Expression QTL analysis of established colorectal cancer risk variants in colon tumors and adjacent normal tissue

Genome-wide association studies (GWAS) have identified 19 risk variants associated with colorectal cancer. As most of these risk variants reside outside the coding regions of genes, we conducted cis-expression quantitative trait loci (cis-eQTL) analyses to investigate possible regulatory functions on the expression of neighboring genes. Forty microsatellite stable and CpG island methylator phenotype-negative colorectal tumors and paired adjacent normal colon tissues were used for genome-wide SNP and gene expression profiling. We found that three risk variants (rs10795668, rs4444235 and rs9929218, using near perfect proxies rs706771, rs11623717 and rs2059252, respectively) were significantly associated (FDR q-value ≤0.05) with expression levels of nearby genes (<2 Mb up- or down-stream). We observed an association between the low colorectal cancer risk allele (A) for rs10795668 at 10p14 and increased expression of ATP5C1 (q = 0.024) and between the colorectal cancer high risk allele (C) for rs4444235 at 14q22.2 and increased expression of DLGAP5 (q = 0.041), both in tumor samples. The colorectal cancer low risk allele (A) for rs9929218 at 16q22.1 was associated with a significant decrease in expression of both NOL3 (q = 0.017) and DDX28 (q = 0.046) in the adjacent normal colon tissue samples. Of the four genes, DLGAP5 and NOL3 have been previously reported to play a role in colon carcinogenesis and ATP5C1 and DDX28 are mitochondrial proteins involved in cellular metabolism and division, respectively. The combination of GWAS findings, prior functional studies, and the cis-eQTL analyses described here suggest putative functional activities for three of the colorectal cancer GWAS identified risk loci as regulating the expression of neighboring genes.

Unique DNA methylome profiles in CpG island methylator phenotype colon cancers

A subset of colorectal cancers was postulated to have the CpG island methylator phenotype (CIMP), a higher propensity for CpG island DNA methylation. The validity of CIMP, its molecular basis, and its prognostic value remain highly controversial. Using MBD-isolated genome sequencing, we mapped and compared genome-wide DNA methylation profiles of normal, non-CIMP, and CIMP colon specimens. Multidimensional scaling analysis revealed that each specimen could be clearly classified as normal, non-CIMP, and CIMP, thus signifying that these three groups have distinctly different global methylation patterns. We discovered 3780 sites in various genomic contexts that were hypermethylated in both non-CIMP and CIMP colon cancers when compared with normal colon. An additional 2026 sites were found to be hypermethylated in CIMP tumors only; and importantly, 80% of these sites were located in CpG islands. These data demonstrate on a genome-wide level that the additional hypermethylation seen in CIMP tumors occurs almost exclusively at CpG islands and support definitively that these tumors were appropriately named. When these sites were examined more closely, we found that 25% were adjacent to sites that were also hypermethylated in non-CIMP tumors. Thus, CIMP is also characterized by more extensive methylation of sites that are already prone to be hypermethylated in colon cancer. These observations indicate that CIMP tumors have specific defects in controlling both DNA methylation seeding and spreading and serve as an important first step in delineating molecular mechanisms that control these processes.

Clinical characteristics and outcomes in familial adenomatous polyposis patients with a long-term treatment of celecoxib: a matched cohort study

Familial adenomatous polyposis (FAP) is a rare genetic disease. Without treatment, FAP patients have a 100% lifetime risk of developing colorectal cancer. This study was conducted to evaluate the effect of celecoxib treatment in prolonging the time to FAP-related events and to document the safety profile of the long-term use of celecoxib (≥6 months) in FAP patients. FAP patients receiving celecoxib in routine clinical practice were individually matched with historical/concurrent FAP patients not receiving celecoxib. The study population included patients aged 12 years or older registered in national and regional FAP registries in Denmark, the United States, Spain, and Canada. Descriptive statistics were used to summarize dose and duration among celecoxib treated patients. The primary study endpoints, time-to-next-FAP events, were examined with Kaplan-Meier method. Fifty four celecoxib-treated patients were recruited and a matched control was identified for 13 of these patients. The Kaplan-Meier estimated probability of not having a polypectomy 12 and 60 months post- ileorectal anastomosis in the celecoxib-treated patients (n = 33) was 60.6% and 42.2%, respectively. The estimated probability of not having a polypectomy 6-60 months post-ileal pouch-anal anastomosis the celecoxib-treated patients (n = 24) was 100%. The median total daily dose of celecoxib was 698.9 mg with the majority treated more than 24 months. Five celecoxib-treated patients experienced 6 serious adverse events with one of these events (rash) considered related to celecoxib. Long term celecoxib treatment appeared to be well tolerated in FAP patients with or without FAP-related surgeries.

Relative role of methylator and tumor suppressor pathways in ulcerative colitis-associated colon cancer

BACKGROUND

Chronic ulcerative colitis (UC) is associated with an increased colorectal cancer risk which may be secondary to repetitive mucosal injury. Both epigenetic methylation and the classic adenoma-to-carcinoma sequence have been implicated in this malignant transformation, but the underlying molecular mechanisms remain poorly defined. This study compares the molecular characteristics of colitis-associated and common colorectal cancers.

METHODS

Nineteen patients with colorectal adenocarcinomas arising within UC were matched for age and cancer site with 54 patients with sporadic adenocarcinomas. Tumor tissue was examined for BRAF mutations, CpG island methylator phenotype (CIMP), and MLH1 promoter methylation. Mutations of KRAS and p53 were assessed by sequencing.

RESULTS

Patient demographics were similar for the two groups. CIMP was observed in 22% of sporadic colorectal cancers and in 5% of UC cancers (P = 0.162). Rates of BRAF mutation (4% vs 5%, P = 1.0), MLH1 methylation (9% versus 5%, P = 0.682), and KRAS mutations (24% versus 32%, P = 0.552) were similar between the groups. However, colitis-associated colorectal cancers were more likely to have a p53 mutation compared to sporadic adenocarcinomas (95% versus 53%, P = 0.001). The dominant mutation for colitis-associated cancers was a mutation in codon 4, representing half of the mutations. Furthermore, colitis-associated cancers had a higher rate of mutation in codon 8 (48% versus 6%, P < 0.001) than sporadic counterparts.

CONCLUSIONS

Unlike other inflammatory gastrointestinal cancers, colitis-associated colorectal cancers do not preferentially arise via a methylator pathway when compared to sporadic colorectal cancers. Chromosomal instability remains an important etiology, but with a unique p53 frequency and mutation pattern.

Metachronous colorectal cancer risk for mismatch repair gene mutation carriers: the advantage of more extensive colon surgery

BACKGROUND

Surgical management of colon cancer for patients with Lynch syndrome who carry a mismatch repair (MMR) gene mutation is controversial. The decision to remove more or less of the colon involves the consideration of a relatively high risk of metachronous colorectal cancer (CRC) with the impact of more extensive surgery.

OBJECTIVE

To estimate and compare the risks of metachronous CRC for patients with Lynch syndrome undergoing either segmental or extensive (subtotal or total) resection for first colon cancer.

DESIGN

Risk of metachronous CRC was estimated for 382 MMR gene mutation carriers (172 MLH1, 167 MSH2, 23 MSH6 and 20 PMS2) from the Colon Cancer Family Registry, who had surgery for their first colon cancer, using retrospective cohort analysis. Age-dependent cumulative risks of metachronous CRC were calculated using the Kaplan-Meier method. Risk factors for metachronous CRC were assessed by a Cox proportional hazards regression.

RESULTS

None of 50 subjects who had extensive colectomy was diagnosed with metachronous CRC (incidence rate 0.0; 95% CI 0.0 to 7.2 per 1000 person-years). Of 332 subjects who had segmental resections, 74 (22%) were diagnosed with metachronous CRC (incidence rate 23.6; 95% CI 18.8 to 29.7 per 1000 person-years). For those who had segmental resections, incidence was statistically higher than for those who had extensive surgery (P <0.001). Cumulative risk of metachronous CRC was 16% (95% CI 10% to 25%) at 10 years, 41% (95% CI 30% to 52%) at 20 years and 62% (95% CI 50% to 77%) at 30 years after segmental colectomy. Risk of metachronous CRC reduced by 31% (95% CI 12% to 46%; p=0.002) for every 10 cm of bowel removed.

CONCLUSIONS

Patients with Lynch syndrome with first colon cancer treated with more extensive colonic resection have a lower risk of metachronous CRC than those receiving less extensive surgery. This finding will better inform decision-making about the extent of primary surgical resection.

Influence of age at ileoanal pouch creation on long-term changes in functional outcomes

AIM

We reviewed the functional results and quality of life (QOL) of patients who had had an ileoanal pouch (IPAA) for at least 15 years.

METHOD

Retrospective analysis was undertaken of data accrued prospectively into a pouch database since 1983. Patients who had retained an IPAA for at least 15 years were identified. Trends in IPAA function and QOL of the patients were determined over a time-period of 15 years after formation of the IPAA. Data were compared for patients who were < 35, 35-55 and > 55 years of age when the IPAA was formed.

RESULTS

Three hundred and ninety-six of a total of 3276 patients in the database (53% men, median age 36 years and median follow-up 17.1 years) underwent IPAA with at least 15 years of follow-up. The final pathology was ulcerative colitis in 78%; 66.4% of patients had a restorative proctocolectomy, 91.4% underwent temporary diversion, 59% had a J-pouch configuration and 63.1% a stapled anastomosis. The frequency of bowel movements remained the same over the follow-up period. There was an increase in the incidence of incontinence and urgency after 15 years with no significant change in dietary, social, work and sexual restrictions during follow-up. Patients in all three age groups experienced deterioration in pouch function at 15 years of follow up compared with the function at 5 years. The QOL of the patients remained high and stable.

CONCLUSION

There is a deterioration of pouch function after 15 years, irrespective of the age of the patient when the IPAA was formed. Despite this, QOL appears to be high for all patients who retain their pouch.

The PREMM(1,2,6) model predicts risk of MLH1, MSH2, and MSH6 germline mutations based on cancer history

BACKGROUND & AIMS

We developed and validated a model to estimate the risks of mutations in the mismatch repair (MMR) genes MLH1, MSH2, and MSH6 based on personal and family history of cancer.

METHODS

Data were analyzed from 4539 probands tested for mutations in MLH1, MSH2, and MSH6. A multivariable polytomous logistic regression model (PREMM(1,2,6)) was developed to predict the overall risk of MMR gene mutations and the risk of mutation in each of the 3 genes. The discriminative ability of the model was validated in 1827 population-based colorectal cancer (CRC) cases.

RESULTS

Twelve percent of the original cohort carried pathogenic mutations (204 in MLH1, 250 in MSH2, and 71 in MSH6). The PREMM(1,2,6) model incorporated the following factors from the probands and first- and second-degree relatives (odds ratio; 95% confidence intervals [CIs]): male sex (1.9; 1.5-2.4), a CRC (4.3; 3.3-5.6), multiple CRCs (13.7; 8.5-22), endometrial cancer (6.1; 4.6-8.2), and extracolonic cancers (3.3; 2.4-4.6). The areas under the receiver operating characteristic curves were 0.86 (95% CI, 0.82-0.91) for MLH1 mutation carriers, 0.87 (95% CI, 0.83-0.92) for MSH2, and 0.81 (95% CI, 0.69-0.93) for MSH6; in validation, they were 0.88 for the overall cohort (95% CI, 0.86-0.90) and the population-based cases (95% CI, 0.83-0.92).

CONCLUSIONS

We developed the PREMM(1,2,6) model, which incorporates information on cancer history from probands and their relatives to estimate an individual's risk of mutations in the MMR genes MLH1, MSH2, and MSH6. This Web-based decision making tool can be used to assess risk of hereditary CRC and guide clinical management.