Family History of Colorectal Cancer in BRAF p.V600E-Mutated Colorectal Cancer Cases

Colorectal cancer (CRC) is a major cause of morbidity and mortality worldwide (1), being the third most common cancer globally and the fourth most common cancer-related death. CRC has a strong familial component with 10% to 20% of cases attributed to having a family history of the disease, depending on the age at diagnosis (2, 3). However, only 2% to 5% of all CRC arise in the setting of the highly penetrant inherited syndromes, namely Lynch syndrome (caused by mutations in the MLH1, MSH2, MSH6, and PMS2 genes), and the adenomatous and hamartomatous polyposis syndromes (mutations in the APC, MutYH, STK11, SMAD4, BMPR1A, and PTEN genes; ref. 4). An estimated 30% to 50% of the excess genetic risk of CRC associated with a family history cannot, as yet, be attributed to mutations within the known CRC-predisposing genes (5). Determining molecular markers that are associated with, or can identify, an increase in risk for the relatives of CRC cases is a plausible first step in unraveling the remaining hereditary component of CRC.

The BRAF c.1799T>A p.V600E somatic mutation (hereafter referred to as BRAF p.V600E or BRAF-mutated) is present in approximately 10% to 20% of all CRC tumors and 30% to 75% of CRC mismatch repair-deficient (MMR-deficient) tumors that show high levels of microsatellite instability (MSI-H; refs. 6, 7). The BRAF p.V600E mutation is strongly associated with widespread DNA methylation (CpG island methylator phenotype or CIMP) and tumor development via the serrated neoplasia pathway (7–9). As such, the BRAF p.V600E mutation is rarely seen in MMR-deficient CRCs that develop via the adenoma–carcinoma pathway as a result of germline mismatch repair (MMR) gene mutations (Lynch syndrome; ref. 10). To date, the clinical use of finding a BRAF p.V600E mutation has been to exclude Lynch syndrome in CRCs that show loss of the MLH1 and PMS2 proteins by immunohistochemistry (IHC). Although multiple reports suggest that the BRAF p.V600E mutation is a predictor of poor prognosis in MMR-proficient CRC (11–14), such testing is not currently in routine use.

In addition to its occurrence in CRCs from individuals with no family history of CRC (7), the BRAF p.V600E mutation is frequently observed in the CRCs from multiple relatives within families with serrated neoplasia predispositions such as Jass syndrome (15, 16, 18) and serrated polyposis (17, 20). Previous studies have shown a positive association of family history of both CRC and extracolonic cancers (ECC) with risk of a BRAF-mutated CRC (11, 18, 19). These studies included CRC-affected individuals across a broad range of age at diagnosis. In the population, the familial relative risks for CRC are highest when 1 or more first-degree relatives are diagnosed with CRC under the age of 50 years, with the relative risk only slightly reduced when CRC is diagnosed between 50 and 59 years of age (20). Therefore, in this study, we investigated associations of a family history of CRC and ECCs with the BRAF p.V600E mutation status of CRC using probands with CRC diagnosed before 60 years of age.

Population-based incident CRC cases (probands) diagnosed in Victoria between 1997 and 2007 were recruited to the Australasian Colorectal Cancer Family Registry (ACCFR; ref. 21). Of these, we identified 959 probands with primary adenocarcinoma of the colon or rectum (ICD-O-3 codes C180-C189, C199, and C209; refs. 22, 24) during 2 recruitment periods. Phase I recruitment of patients with CRC diagnosed between 1997 and 2001 included all patients with a CRC diagnosed between 18 and 44 years of age and 50% of cases with CRC diagnosed between the ages of 45 and 59 years. Phase II recruitment of patients with CRC diagnosed between 2001 and 2006 included all patients with a CRC diagnosed between 18 and 49 years of age. Recruitment of probands to the ACCFR was not dependent on family history. All first- and second-degree relatives (FDR and SDR) of the proband, and all FDRs of additional CRC-affected family members were recruited where possible. Written informed consent was obtained from all participants to collect a blood sample and tumor pathology materials (tumor blocks and diagnostic slides). This study was approved by the Human Research Ethics Committees (QIMR HREC) under protocol P628 of all participating institutions.

Information on personal and family history of CRC and ECCs (defined as any cancer history in FDRs and/or SDRs), was obtained from completion of a baseline questionnaire completed at recruitment and then verified, where possible, using pathology reports, medical records, cancer registry reports, and/or death certificates. Probands and relatives were either actively or passively followed-up every 4 to 5 years from initial enrolment, including updating information on the number, sex, and birthdates of relatives (parents, siblings, and children), their cancer history, vital status, and, if deceased, date of death by linkage to tumor registries and death indices. All cancers, except for nonmelanoma skin cancers, were recorded with dates of diagnosis. The present study was based on all available baseline and follow-up data such that 49% of all reported CRCs in relatives were confirmed by pathology report, hospital or clinic record, death certificate, or cancer registry.

Primary CRC tissue from the Jeremy Jass Memorial Tissue Bank was available for 819 of the probands for pathology review and molecular characterization. CRCs were reviewed by specialist gastrointestinal pathologists for site, tumor grade, tumor margin, presence of mucinous component, peritumoral lymphocytes, Crohn-like lymphocytic reaction, tumor-infiltrating lymphocytes, and synchronous CRC. In probands with synchronous CRCs, 1 CRC was randomly selected where both were available for testing. Tumors from the ileocecal junction through the cecum, ascending colon, hepatic flexure, and transverse colon were grouped as right-sided (proximal) colon cancers (ICD-O-3 codes C180, C182, C183, and C184). Tumors in the splenic flexure (C185), descending (C186), sigmoid colon (C187) and rectosigmoid junction (C199) were classified as left-sided (distal) colon cancers, with tumors in the rectum (C209) considered as a third distinct group.

The CRCs of probands were characterized for MMR deficiency by MSI using a 10-marker panel and/or by IHC for the 4 MMR proteins as has been previously described (23–25). Tumors were described as: (i) MMR-deficient if they were MSI-H and showed loss of expression of 1 or more of the MMR proteins by IHC; or (ii) MMR-proficient if tumors were microsatellite stable (MSS) or MSI-L (low-level MSI) or showed stable expression of all 4 MMR proteins by IHC. CRCs where both MSI and MMR immunohistochemical testing was completed (486/819, 59.3%) showed 99.8% concordance between MSI and MMR IHC results (1 CRC was discordant and excluded); therefore, CRCs were categorized as MMR-proficient or -deficient using results from either MSI or immunohistochemical testing or both. In addition, tumors showing loss of the MLH1 protein by IHC (with or without the loss of PMS2) were characterized for methylation of the MLH1 promoter using the MethyLight assay as previously described (26, 27). Probands with CRC that showed MMR-deficiency through loss of expression of 1 or more of the MMR proteins by IHC and/or those who had 30% or more of the markers showing instability (MSI-H) underwent germline mutation testing (Sanger sequencing and Multiplex ligation-dependent probe amplification; refs. 21, 24). MMR mutation testing was carried out as previously described (21, 27–30). All probands were screened for mutations in the MUTYH gene as previously described (31). Probands identified with Lynch Syndrome or MUTYH mutation carriers by genetic testing were excluded from the analysis. Individuals with CRCs that showed loss of MMR protein by IHC but did not have an identified MMR gene mutation and were also negative for both the BRAF p.V600E mutation (BRAF-wild-type) and MLH1 promoter methylation were considered probable Lynch syndrome cases and were also excluded from the study. The final CRC cases included in this study were either (i) MMR-proficient as determined by either MMR IHC or MSI testing or (ii) showed loss of MLH1 and PMS2 proteins by IHC and were MLH1 methylated and/or BRAF p.V600E mutated.

A fluorescent allele-specific PCR assay was used to detect the somatic T>A mutation at nucleotide 1799 (c.1799T>A p.V600E) in exon 15 of the BRAF gene as has been previously described (32).

Unconditional logistic regression was carried out to estimate odds ratios (OR) and their 95% confidence intervals (CI) for the associations between predictor variables (including family history of CRC or ECCs) and CRC with BRAF p.V600E mutation after adjusting for sex and age at diagnosis. Compared with BRAF-WT CRCs (the referent group), associations were assessed for MMR-proficient and MMR-deficient BRAF-mutated CRCs. The association between family history of CRC in FDR and SDR (yes/no) and age at diagnosis of CRC (per year) was assessed in probands with BRAF-mutated CRCs after adjusting for sex. The mean age at diagnosis of CRCs were compared using Student t test and ANOVA between males and females, subjects with MMR-deficient and MMR-proficient tumors, those with or without family history of CRC, and those with or without family history of ECC for BRAF-WT and BRAF-mutated CRC cases separately. All individuals with missing data for any variable were excluded from the analysis. All statistical analyses were conducted using Stata 11.0 (StataCorp. Stata Statistical Software: Release 11.: StataCorp LP; 2009).

A total of 959 eligible probands were recruited to the ACCFR. Of these, primary CRC tissue was available for molecular characterization for 819 probands (85.4%). Mutation testing identified 55 probands with a germline mutation in 1 of the MMR-genes, 4 with biallelic MutYH mutations, and 11 with monoallelic MutYH mutations, all of whom were excluded from analysis. As noted, probands with CRCs showing loss of MSH2 and MSH6, or solitary loss of MSH6 or PMS2 by IHC without an identified MMR gene mutation or that could not have germline testing carried out (no blood-derived DNA), as well as probands with MLH1- and PMS2-deficient CRCs that were BRAF-WT and without evidence of MLH1 promoter methylation were also excluded from the study as these findings strongly suggest the presence of an undetected germline mutation (total number of MMR-deficient suspected Lynch syndrome probands excluded = 59). The characteristics of the final sample set comprising 690 probands are described in Table 1, where 343 (49.7%) were female. The average age at diagnosis of CRC was 46.9 ± 7.8 years, with a range between 18 and 60 years.

The BRAF p.V600E mutation was present in CRCs from 53 of 690 probands (7.7%); 44 of these (83%) were MMR-proficient. Seventeen percent of the 53 BRAF-mutated CRCs showed MMR deficiency (9/53) compared with 0.8% (5/637) of BRAF-WT CRCs (OR, 38.73; 95% CI, 11.48–130.67; P < 0.001; Table 1). Overall, there was no statistically significant difference in age at diagnosis of CRC between BRAF-mutated and BRAF-WT CRCs (Table 1). However, probands with MMR-proficient, BRAF-mutated CRC had an earlier age at diagnosis compared with those with a BRAF-WT CRC (44.5 ± 9.2 years vs. 47.1 ± 7.7 years), and the OR per year of age at diagnosis was 0.96 (95% CI, 0.92–0.99; P = 0.02; Table 1). In contrast, the association of age at diagnosis for MMR-deficient, BRAF-mutated CRCs (51.4 years ± 8.6 years) compared with BRAF-WT CRC (47.1 ± 7.7 years; P = 0.09) showed an OR per year of age at diagnosis of 1.10 (95% CI, 0.99–1.22; P = 0.08; Table 1).

Compared with BRAF-WT CRC, BRAF-mutated CRCs were more likely to have MMR-deficient CRCs (OR, 38.73; 95% CI, 11.48–130.67; P < 0.001), MLH1 promoter methylation (OR, 27.42; 95% CI, 3.18–236.08; P = 0.003), high-grade CRCs (OR, 4.12; 95% CI, 2.28–7.44; P < 0.001), an infiltrative margin (OR, 1.99; 95% CI, 1.09–3.62; P = 0.02), and increased levels of tumor-infiltrating lymphocytes (TILs; P = 0.003; Table 1). Compared with BRAF-WT CRC, MMR-deficient BRAF-mutated CRCs were more likely to be in the right colon (OR, 6.01; 95% CI, 1.46–24.71; P = 0.01), have Crohn-like reactions (OR, 9.46; 95% CI, 2.15–41.66; P = 0.003), and TILs (P < 0.001; Table 1). Compared with BRAF-WT CRC, MMR-proficient BRAF-mutated CRCs were more likely to be high grade (OR, 4.38; 95% CI, 2.30–8.32; P < 0.001) and have an infiltrative margin (OR, 2.86; 95% CI, 1.46–5.61; P = 0.002). We observed no evidence of associations between BRAF-mutated CRCs and the presence of a mucinous component, peritumoral lymphocytes, or synchronous CRCs, even after stratification by MMR status (Table 1).

In this study group, approximately one-third of probands with a BRAF-mutated CRC reported having a FDR or SDR with CRC (18/53); therefore, we analyzed the probands' age at diagnosis and tumor MMR status to assess the association between a family history of CRC and the odds of a BRAF-mutated CRCs stratified by these features. The mean age at diagnosis of a BRAF-mutated CRC was significantly greater statistically for probands with a family history of CRC (49.3 ± 6.4 years) than for probands without a family history of CRC (43.8 ± 10.2 years; P = 0.04; Table 2). The odds of having family history of CRC in FDR and SDR were 9% higher per year of age in probands with BRAF-mutated CRCs (OR, 1.09; 95% CI, 1.00–1.18; P = 0.04). In comparison, the odds of having a family history of CRC in FDR and SDR was 2% higher per year of age in probands with BRAF-WT CRCs (OR, 1.02; 95% CI, 1.00–1.04; P = 0.04), where the mean age at diagnosis for probands with a BRAF-WT CRC with and without a family history of CRC was 47.7 years ± 7.1 years versus 46.5 ± 8.1 years (P = 0.04; Table 2).

Of all 690 probands, 160 (23.2%) had at least 1 FDR with CRC and 331 (48%) had at least 1 FDR or SDR with CRC. Sixty-five probands had both a FDR and SDR with CRC (9.4%), and only 1 of these had a BRAF-mutated CRC (1/65; 1.5%). Compared with probands with a BRAF-WT CRC, probands with a BRAF-mutated CRC were less likely to have a FDR with CRC (OR, 0.41; 95% CI, 0.17–0.99; P = 0.05) or FDR or SDR with CRC (OR, 0.55; 95% CI, 0.30–1.00; P = 0.05). The inverse relationship between family history of CRC and BRAF p.V600E mutation was evident for MMR-proficient CRCs (OR, 0.46; 95% CI, 0.24–0.91; P = 0.03) but not for MMR-deficient CRCs (OR, 1.20; 95% CI, 0.32–4.53; P = 0.79; Table 3).

There was no evidence that the occurrence of ECCs in FDRs or SDRs was associated with having a BRAF-mutated CRC (Table 4). Stratification by MMR status did not reveal any significant associations between family history of ECC and BRAF-mutated CRC (Table 4). There was no evidence of difference in mean age at diagnosis of CRC in probands with and without a family history of ECCs (Table 2).

BRAF p.V600E testing has shown considerable efficacy in its triage of MLH1-deficient CRCs into Lynch syndrome and non-Lynch syndrome classes (33). The implication of a positive BRAF p.V600E mutation test is that the family concerned are not harboring a MMR gene mutation and, therefore, did not require any additional surveillance over and above routine recommendations. However, recent evidence has suggested that the relatives of individuals with a BRAF p.V600E-mutated CRC are at an increased risk of CRC and possibly ECCs (16, 18, 19, 34). This was also observed for the relatives of individuals with a MLH1 promoter hypermethylated CRC (35), a tumor feature highly correlated with the BRAF p.V600E mutation. In addition, multicase families, with a predisposition to develop advanced serrated lesions (polyps and CRC) and a high frequency of CRC with the BRAF p.V600E mutation and variable levels of MSI (MSI-V), have been described (16). In a study of 11 such families, we have shown that 7 had linkage to the same region of chromosome 2q32.2-q35 (15) supporting a genetic predisposition to develop serrated neoplasia.

Population-based studies have supported the concept of a familial predisposition associated with BRAF-mutated CRC. Samowitz and colleagues (11) observed that MSS BRAF p.V600E-mutated CRCs were more likely to have a family history of CRC compared with BRAF-WT CRCs (OR, 4.23; 95% CI, 1.65–10.84). CRCs with the BRAF p.V600E mutation were also shown to be statistically significantly increased in families with both CRC and ECCs when compared with families affected only with CRC (17.5% vs. 3.5%, P = 0.009; ref. 19). Recently, Wish and colleagues (18), observed an elevated risk of CRC for FDRs of index patients with CRC showing MSI-H and the BRAF p.V600E mutation (HR, 2.49; 95% CI, 1.57–3.93) and with MSS and the BRAF p.V600E mutation (HR, 1.64; 95% CI, 1.01–2.66) compared with FDRs of index patients with MSS, BRAF-WT tumors. Together, these 3 studies support an association between a family history of CRC and an increased risk of the BRAF-mutated CRC.

In contrast, our current study of CRC diagnosed before age 60 from the Australasian Colorectal Cancer Family Registry showed that family history of CRC was not associated with an increased risk of the BRAF p.V600E mutation in CRC, even after stratification by MMR status. Instead, our results showed that a FDR or SDR with CRC was associated with a lower risk of early-onset, BRAF-mutated CRC. One potential explanation for the discrepancy in findings between this study and the previous reports is the difference in the mean age at diagnosis of the CRC cases. One of the key findings in our study was that the mean age at diagnosis of a BRAF-mutated CRC was significantly greater statistically (P = 0.04) for probands with a family history of CRC (49.3 ± 6.4 years) compared with probands without a family history of CRC (43.8 ± 10.2 years) and that the odds of having a family history of CRC (FDR or SDR) were 9% higher per year (P = 0.04) for probands with a BRAF-mutated CRC. The ACCFR recruited population-based cases diagnosed at the age of60 or younger (65% diagnosed before 50 years of age) and, therefore, probands with a BRAF-mutated CRC were necessarily young, with a mean age at diagnosis of 45.7 ± 9.4 years. In contrast, probands with a BRAF p.V600E-mutated CRC described in the study by Wish and colleagues (18) had a mean age at diagnosis of 61.5 ± 7.3 years for MSS CRC and 66.2 ± 6.4 years for MSI-H CRC (overall cohort mean age at diagnosis of 59.9 years). Similarly, in the study by Samowitz and colleagues (11), 85% of probands with a BRAF-mutated MSS CRC were older than 55 years of age at diagnosis and 97.5% of probands with a BRAF-mutated MSI-H CRC were older than 55 years of age at diagnosis. Taken together, our data and these studies suggest that a family history of CRC may be more common in older persons with a BRAF p.V600E-mutated CRC.

Alternatively, hereditary factors may be more pronounced in early-onset CRC cases that are BRAF- WT, as supported by the inverse association between family history of CRC and the BRAF p.V600E mutation in this study. If we considered the alternative analytic approach with the BRAF p.V600E-mutated CRC cases as the reference group, the risk of having a FDR with CRC in this early-onset CRC study would be increased 2.5-fold for the BRAF-WT CRC cases. This is consistent with BRAF p.V600E mutations in early-onset CRC cases being caused by factors that are not correlated or shared by relatives; that is, BRAF p.V600E mutation in early-onset CRC is a marker for noninherited CRC risk. Almost half of the probands with early-onset BRAF-WT CRC reported a FDR or SDR with CRC, suggesting that these cases may be influenced by more highly penetrant genetic factors resulting in a more prevalent familial clustering of CRC. In comparison, only a third of the probands with early-onset BRAF-mutated CRC reported a FDR or SDR with CRC. A further study comparing the incidence of a family history of CRC in BRAF p.V600E-mutated cases to that of the general population may provide evidence for any elevated risk of CRC in relatives above that of the general population without the potential confounding influence of early-onset CRC cases that are BRAF-WT. There is some evidence that this alternate approach would identify an elevated risk of CRC, and possibly ECCs, in relatives of probands with a BRAF-mutated CRC based on the findings of a recent study that showed an increased risk of CRC as well as stomach cancer and possibly ovarian and liver cancer in relatives of CRC cases with methylation of the MLH1 gene promoter (35). The overlap between MLH1 methylation and BRAF p.V600E mutation is reported to be up to 75% in all CRC (10, 36), and lends further support to heritable factors that influence the risk of CRC developing via the serrated neoplasia pathway.

Among the probands in this study with a BRAF p.V600E-mutated CRC, only 31.7% reported having a FDR or SDR with CRC, suggesting that there is potential heterogeneity of familial risk within BRAF-mutated CRCs. Stratifying by MMR status provided evidence that probands with MMR-proficient, BRAF-mutated CRC were less likely to have a family history of CRC. In contrast, there was no evidence of MMR-deficient, BRAF-mutated CRCs associated with a family history of CRC. The identification of further markers of an increased risk of CRC in relatives is needed; histopathologic features that differ between BRAF-mutated CRC with and without a family history of CRC may be useful. However, this was beyond the scope of this study because of the small number of BRAF-mutated CRC cases but it warrants further investigation in a larger study.

Recently, lower levels of methylation or hypomethylation of the LINE-1 repetitive DNA element was shown to be associated with a family history of CRC (37–39) and with earlier onset CRC (38, 40). Previous studies have established an inverse association between LINE-1 hypomethylation and CRC characterized by low levels of CIMP (CIMP-low/negative), MSS, and BRAF-WT (38, 41). Together, the results from our study and those previously reported support a subgroup of CRC that is likely to be enriched for a family history of CRC and would be molecularly defined by BRAF-WT, MSS, CIMP-low/negative, and LINE-1 hypomethylation, presenting at an earlier age at diagnosis and it further highlights the importance of molecular pathologic epidemiologic studies in CRC (42).

The frequency of BRAF-mutated CRCs was 7.7% in this study, with only 17% of these tumors showing MMR deficiency. This finding is in contrast to previous studies that have described both a higher frequency of the BRAF p.V600E mutation in CRC, between 10% and 17% of CRCs tested in large cohort or population-based studies, and a higher proportion of BRAF-mutated CRCs having MMR-deficiency, reporting between 42% and 52% in these same studies (11, 18, 43). The discrepancy in frequency of both these features between previous studies and ours is likely due to differences in the mean age at diagnosis of the probands, because both the BRAF p.V600E mutation and MMR deficiency as a result of MLH1 promoter methylation are strongly associated with increasing age at diagnosis (44). In support of this, we observed probands with MMR-deficient BRAF-mutated CRCs to be significantly older statistically than probands with MMR-proficient, BRAF-mutated CRCs, a finding also consistent with a previous report (11).

The strength of this study is that it is a population-based cohort of incident early-onset CRC cases who have been well characterized for molecular and genetic indications of Lynch syndrome and MUTYH mutations. Family history was collected in a systematic manner and attempts were made to validate reports from medical records, cancer registration, and death certification. However, the small number of BRAF p.V600E-mutated CRCs (n = 53) in this study, particularly those that were MMR-deficient, represents a limitation of the study.

In conclusion, we identified a novel inverse association between a family history of CRC and early-onset BRAF p.V600E-mutated CRCs. The previous study cohorts that identified a significantly increased risk of CRC for relatives were substantially older at diagnosis than this study cohort. Furthermore, our findings suggest that relatives of early-onset, BRAF-mutated, and MMR-deficient CRC cases do not require additional surveillance. However, despite a large number of total incident cases, these results should be interpreted with caution as the numbers of BRAF-mutated CRCs that were MMR-deficient, were relatively low. We did observe that, despite an inverse relationship between BRAF-mutated CRC and family history in the youngest-onset probands, family history prevalence was significantly associated with increasing age at diagnosis when the proband had a BRAF-mutated CRC. Therefore, relatives of older patients presenting with a BRAF p.V600E-mutated CRC may be at an increased risk of CRC, as has been suggested by the results of Levine and colleagues (35–37). Larger studies are needed to explore this risk, stratified by age. We found no evidence that probands with a BRAF p.V600E-mutated CRC were more or less likely to report a family history of ECC than were those with BRAF-WT CRC. These data provide useful insights into cancer risk assessment and heterogeneity within families and should facilitate colonoscopic screening for those with an increased risk of CRC.

The content of this article does not necessarily reflect the views or policies of the National Cancer Institute or any of the collaborating centers in the Cancer Family Registries, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government or the Cancer Family Registry. Authors had full responsibility for the design of the study, collection of the data, analysis and interpretation of the data, the decision to submit the article for publication, and the writing of the article.

No potential conflicts of interest were disclosed.

Conception and design: D.D. Buchanan, A.K. Win, M.D. Walsh, F. Macrae, G.G. Giles, J.L. Hopper, J.P. Young

Development of methodology: D.D. Buchanan, A.K. Win, J.L. Hopper

Acquisition of data (provided animals, acquired and managed patients, provided facilities, etc.): D.D. Buchanan, M.D. Walsh, R.J. Walters, M. Clendenning, F. Macrae, J. Arnold, I. Winship, J.D. Potter, J.L. Hopper, M.A. Jenkins

Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis): D.D. Buchanan, A.K. Win, R.J. Walters, M. Clendenning, F. Macrae, N.M. Lindor, J.L. Hopper, C. Rosty, J.P. Young, M.A. Jenkins

Writing, review, and/or revision of the manuscript: D.D. Buchanan, A.K. Win, M.D. Walsh, M. Clendenning, F. Macrae, S. Parry, J. Arnold, I. Winship, G.G. Giles, N.M. Lindor, J.D. Potter, J.L. Hopper, C. Rosty, J.P. Young, M.A. Jenkins

Administrative, technical, or material support (i.e., reporting or organizing data, constructing databases): D.D. Buchanan, M.D. Walsh, R.J. Walters, B.N. Nagler, S.-A. Pearson, N.M. Lindor, J.L. Hopper

Study supervision: D.D. Buchanan, J.D. Potter, J.L. Hopper

The authors thank all study participants of the Australasian Colon Cancer Family Registry and study co-ordinator Judi Maskiell, data managers Erika Pavluk, Kelly Aujard, Maggie Angelakos, and David Packenas, and participant interviewers for their contributions to this project. The authors also thank Professor John Baron for his assistance with statistical interpretation and presentation of the findings and acknowledge the contributions of the late Professor Jeremy Jass to the study including carrying out pathology reviews for cases.

This work was financially supported by a NHMRC project grant 1025799 and by the National Cancer Institute, NIH under RFA #CA-95-011 and through cooperative agreements with members of the Colon Cancer Family Registry and Principal Investigators of Australasian Colorectal Cancer Family Registry (U01 CA097735).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.