Familial colorectal adenocarcinoma and hereditary nonpolyposis colorectal cancer: a nationwide epidemiological study from Sweden

Posttranslational modifications as therapeutic targets for intestinal disorders

A variety of biological processes are regulated by posttranslational modifications. Posttranslational modifications including phosphorylation, ubiquitination, glycosylation, and proteolytic cleavage, control diverse physiological functions in the gastrointestinal tract. Therefore, a better understanding of their implications in intestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, celiac disease, and colorectal cancer would provide a basis for the identification of novel biomarkers as well as attractive therapeutic targets. Posttranslational modifications can be common denominators, as well as distinct biomarkers, characterizing pathological differences of various intestinal diseases. This review provides experimental evidence that identifies changes in posttranslational modifications from patient samples, primary cells, or cell lines in intestinal disorders, and a summary of carefully selected information on the use of pharmacological modulators of protein modifications as therapeutic options.

Use of Family History and Genetic Testing to Determine Risk of Colorectal Cancer

Approximately 35% of patients with colorectal cancer (CRC) have a family history of the disease attributed to genetic factors, common exposures, or both. Some families with a history of CRC carry genetic variants that cause CRC with high or moderate penetrance, but these account for only 5% to 10% of CRC cases. Most families with a history of CRC and/or adenomas do not carry genetic variants associated with cancer syndromes; this is called common familial CRC. Our understanding of familial predisposition to CRC and cancer syndromes has increased rapidly due to advances in next-generation sequencing technologies. As a result, there has been a shift from genetic testing for specific inherited cancer syndromes based on clinical criteria alone, to simultaneous testing of multiple genes for cancer-associated variants. We summarize current knowledge of common familial CRC, provide an update on syndromes associated with CRC (including the nonpolyposis and polyposis types), and review current recommendations for CRC screening and surveillance. We also provide an approach to genetic evaluation and testing in clinical practice. Determination of CRC risk based on family cancer history and results of genetic testing can provide a personalized approach to cancer screening and prevention, with optimal use of colonoscopy to effectively decrease CRC incidence and mortality.

Mapping of microsatellite instability in endoscopic normal colon

Genomic instability in colorectal cancer (CRC) occurs as either microsatellite instability (MSI) or chromosomal instability. The present study was aimed at examining the MSI for the MLH1 and MSH2 genes in normal colon and polyps, if detected. Four segments of the colon were sampled in 102 subjects during colonoscopy. DNA samples were analyzed for the MSI status according to the Bethesda consensus panel. Family history of any type of cancer or for colon cancer was present in 44.8% and 9.4% of the individuals, respectively. Forty-eight percent of individuals were microsatellite stable for all five markers at all locations, 20% had low MSI status (MSI-L), and 32% had high MSI status (MSI-H). The frequencies of MSI markers differed significantly from each other (p=0.003). The most frequent positive marker was D17S250. This is the first study which revealed that MSI is present in endoscopically normal-looking colon of normal individuals and, more frequently, in individuals with family histories of CRC. The detection of very early-stage CRC is possible by MSI analysis of DNA mismatch repair genes in colon tissues. This study has revealed crucial information for the use of molecular tests in CRC screening, such as high frequencies of MSI in endoscopically normal colon, which might cause false positivity.

Family history of various cancers and pancreatic cancer mortality in a large cohort

A family history of pancreatic cancer is associated with increased risk of pancreatic cancer, but uncertainty remains about the magnitude of this association, whether it varies by age or smoking and whether a family history of other cancers may also be associated with increased risk. We examined family history of 14 cancers and pancreatic cancer mortality among ~1.1 million men and women in Cancer Prevention Study-II (CPS-II). CPS-II participants completed a questionnaire at enrollment in 1982. During follow-up through 2006, there were 7,306 pancreatic cancer deaths. A family history of pancreatic cancer in a parent or sibling was associated with pancreatic cancer mortality [multivariable adjusted rate ratio (RR) = 1.66, 95% confidence interval (CI) 1.43-1.94]. This association was stronger among participants aged under 60 (RR = 2.89, 95% CI 1.67-5.02) than among participants aged 60 or older (RR = 1.61, 95% CI 1.37-1.88). Weaker associations were observed for family history of stomach cancer (RR = 1.23, 95% CI 1.11-1.37), liver cancer (RR = 1.25, 95% CI 1.10-1.43), and colorectal cancer (RR = 1.12, 95% CI 1.01-1.23). Results from this large prospective study indicate family history of pancreatic cancer is associated with a moderate increase in risk of pancreatic cancer, and also identify associations with the family history of certain other cancers which may be useful in generating hypotheses about shared risk factors.

Design considerations in a sib-pair study of linkage for susceptibility loci in cancer

BACKGROUND

Modern approaches to identifying new genes associated with disease allow very fine analysis of association and can be performed in population based case-control studies. However, the sibpair design is still valuable because it requires few assumptions other than acceptably high penetrance to identify genetic loci.

METHODS

We conducted simulation studies to assess the impact of design factors on relative efficiency for a linkage study of colorectal cancer. We considered two test statistics, one comparing the mean IBD probability in affected pairs to its null value of 0.5, and one comparing the mean IBD probabilities between affected and discordant pairs. We varied numbers of parents available, numbers of affected and unaffected siblings, reconstructing the genotype of an unavailable affected sibling by a spouse and offspring, and elimination of sibships where the proband carries a mutation at another locus.

RESULTS

Power and efficiency were most affected by the number of affected sibs, the number of sib pairs genotyped, and the risk attributable to linked and unlinked loci. Genotyping unaffected siblings added little power for low penetrance models, but improved validity of tests when there was genetic heterogeneity and for multipoint testing. The efficiency of the concordant-only test was nearly always better than the concordant-discordant test. Replacement of an unavailable affected sibling by a spouse and offspring recovered some linkage information, particularly if several offspring were available. In multipoint analysis, the concordant-only test was showed a small anticonservative bias at 5 cM, while the multipoint concordant-discordant test was generally the most powerful test, and was not biased away from the null at 5 cM.

CONCLUSION

Genotyping parents and unaffected siblings is useful for detecting genotyping errors and if allele frequencies are uncertain. If adequate allele frequency data are available, we suggest a single-point affecteds-only analysis for an initial scan, followed by a multipoint analysis of affected and unaffected members of all available sibships with additional markers around initial hits.

Extracolonic cancers associated with hereditary nonpolyposis colorectal cancer in the Utah Population Database

BACKGROUND

The data describing the extracolonic cancers associated with hereditary nonpolyposis colorectal cancer (HNPCC) are variable.

METHODS

We ascertained all Amsterdam I criteria-positive pedigrees (N = 18) in the Utah Population Database (UPDB). We identified the extracolonic cancers in the colorectal cancer cases (N = 65) in these pedigrees, and in their first- (N = 509) and second-degree (N = 1,611) relatives. Standardized morbidity ratios were estimated by comparing the observed rates of extracolonic cancer in defined sets of relatives of probands with population expected rates estimated internally from the UPDB.

RESULTS

The extracolonic cancers observed in significant excess in the 65 Amsterdam I criteria-positive colorectal cancer (CRC) cases in the UPDB were uterine (N = 3, p = 0.003), lip (N = 2, p = 0.007), stomach (N = 2, p = 0.009), female genitalia (N = 1, p = 0.004) and larynx (N = 1, p = 0.05). Extracolonic cancers observed in significant excess in the 509 first-degree relatives of the 65 colorectal cancer (CRC) cases in these Amsterdam I criteria pedigrees included: thyroid (N = 5, p = 0.0002) and prostate (N = 19, p = 0.002). Thyroid cancer (N = 6, p = 0.003) was found in significant excess in the second-degree relatives of the Amsterdam I criteria-positive CRC cases.

CONCLUSIONS

In this population-based examination of the extracolonic cancers at excess in classic HNPCC pedigrees (selected by Amsterdam I criteria) we not only observed many of the same cancers previously reported to be associated with HNPCC in both CRC probands and their relatives, but also identified several previously unreported associations. Although our sample size is small, this study is population based, lacks ascertainment and recall bias, and benefits from uniform, consistent diagnoses of all cancers in a statewide registry.

[Identification and management of HNPCC syndrome (hereditary non polyposis colon cancer), hereditary predisposition to colorectal and endometrial adenocarcinomas]

BACKGROUND

The HNPCC syndrome (hereditary nonpolyposis colon cancer) is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for small intestine, urothelial, ovary, stomach and biliary tract carcinomas. HNPCC syndrome is responsible for 5% of colorectal cancers. Identification and management of this disease are part of a multidisciplinary procedure.

METHODS

Twelve experts have been mandated by the French Health Ministry to analyze and synthesize their consensus position, and the resulting document has been reviewed by an additional group of 4 independent experts.

MAIN RECOMMENDATIONS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a 2-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases. The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks, but other organs being at low lifetime risk, no specific surveillance will be proposed.

Clinical genetic counselling for familial cancers requires reliable data on familial cancer risks and general action plans

Familial cancer clustering, without obvious heritability, poses a major challenge for current cancer risk assessment and management. Reliable determination of familial risks for cancer is important for clinical genetic counselling, but medically verified data on familial risks for many malignancies have been limited. However, the nationwide Swedish Family-Cancer Database allows a reliable characterisation of familial risk for all major neoplasms. Even though alert genetic counsellors and certainly clinical cancer geneticists will consider familial cancer clustering in their purview, the standard medical referral systems, which have already been shown to be poor in capturing and referring families at high risk for heritable cancers, are unlikely to ascertain familial aggregations of other cancers that are not known to belong to an inherited cancer syndrome. The data will be helpful in implementing evidence based guidelines for helping the general medical system to ascertain and refer even familial cancer clusters to cancer genetics professionals.

Clinicopathological and molecular genetic analysis of HNPCC in China

AIM: To explore the clinicopathological and molecular genetic features of hereditary nonpolyposis colorectal cancer (HNPCC) in Chinese population.

METHODS: We collected 16 Chinese HNPCC families from Wenzhou, Zhejiang Province, China. Tumor tissues and peripheral white blood cells were studied using microdissection, microsatellite analysis, immunostaining of hMSH2 and hMLH1 proteins and direct DNA sequencing of hMSH2 and hMLH1 genes.

RESULTS: (1) A total of 50 patients had CRC. Average age at diagnosis of the first CRC was 45.7 years; 40.9% and 28.7% of the CRCs were located proximal to the splenic flexure and in the rectum, respectively. Thirty-eight percent of the colorectal cancer patients had synchronous and metachronous CRC. 34.4% and 25% of the CRCs were poor differentiation cancer and mucinous adenocarcinoma, respectively. Fourteen extracoloni tumors were found, and the hepatic cancer was the most common tumor type. Twenty-one patients whose median survival time was 5.7 years died during 1-23 years. Twenty-nine patients have survived for 1-28 years, 58.6%, 41.4% and 24.1% patients have survived for more than 5, 10 and 15 years, respectively; (2) All nine tumor-tissues showed microsatellite instability (MSI) at more than two loci. Four tumor-tissues lost hMSH2 protein expression and one lost hMLH1 protein expression. Three pathological germline mutations were identified from five genetically analyzed families; two of three mutations had not been reported previously as they were a transition from C to A in exon 14 (codon 743) of hMSH2 and a TTC deletion in exon 14 (codon 530) of hMLH1.

CONCLUSION: Chinese HNPCC have specific clinicopathological features, such as early onset, propensity to involve the proximal colon, and high frequency of multiple CRCs, liver cancer more frequent than endometrial cancer. Chinese HNPCC showed relatively frequent germline mutation of mismatch repair (MMR) genes that correlated closely with high-level MSI and loss of expression of MMR genes protein.

Clinical phenotype and prevalence of hereditary nonpolyposis colorectal cancer syndrome in Chinese population

AIM: To describe systematically the clinical characteristics and phenotype of HNPCC families and the prevalence of HNPCC in the general population of CRC patients in China.

METHODS: HNPCC kindreds and CRC patients were from two sources. One was that we consecutively investigated kindreds and patients by ourselves. And the other was the published Chinese and foreign literature related to Chinese HNPCC syndrome. There were 142 HNPCC families fulfilling AC I and/or AC II including 57 families with detailed data, and 3874 general primary CRC patients in all. All statistical tests were two-sided.

RESULTS: In AC I families, the number of Lynch syndrome I and II families were 25 (47.2%) and 28 (52.8%) respectively. There were 215 patients (82.4%) with CRC, 67 patients (25.7%) with extracolonic cancer and 50 patients (19.2%) with multiple primary cancers. In all CRC patients, multiple primary CRC were in 41 patients (19.1%), and the first-CRC was right-sided colorectal cancer in 143 patients (66.5%) and rectal cancer in 44 patients (20.5%). 8.8% and 19.2% of the first cancer were CRC and extracolonic cancers. Among those patients whose first cancer was CRC, 66.8% and 19.9% were right-sided colorectal cancer and rectal cancer, respectively. The similar results were found in AC II families. Normal distribution was only found in the distribution of the age of diagnosis of the first cancer in both AC I families (coefficient of skewness: u = 0.81, 0.20<0.40<P<0.50; coefficient of kurtosis: u = 1.13, 0.20<P<0.40, α = 0.20) and AC II families (coefficient of skewness: u = 0.63, P>0.5>0.20; coefficient of kurtosis: u = 0.84, 0.20<0.40<P<0.50, α = 0.20), but not found in the distribution of the age of diagnosis of the first CRC. When patients with HNPCC-associated cancer suffered from the first malignant tumor in HNPCC families diagnosed by AC I and AC II, the mean age and median age were 45.1±12.7 years and 44.0 years, 45.2±12.7 years and 44.5 years, respectively. The median age of diagnosis of the first tumor of the patients in the later generation was younger than that in the previous generation. Many extracolonic cancers were found to be associated with HNPCC syndrome. Gastric cancer was the most frequent extracolonic cancer followed by endometrial cancer and hepatocarcinoma. In general population of CRC patients, the prevalence of HNPCC diagnosed by AC I and AC II were 1.3% and 2.2%, respectively.

CONCLUSION: The clinical phenotype and prevalence of Chinese HNPCC syndrome are similar to those of Europeans and Americans. Gastric cancer is the most common extracolonic malignant tumor. The age of diagnosis of the first malignant tumor tends to be increasingly younger in patients with HNPCC-related tumors.

Le syndrome HNPCC (hereditary non polyposis colon cancer) : identification et prise en charge

BACKGROUND

The hereditary non-polyposis colon cancer (HNPCC) syndrome is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for other organs tumors. HNPCC syndrome is responsible for 5% of colorectal cancers.

MAJOR ASPECTS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a two-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases.

FURTHER DEVELOPMENTS

The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks; other organs being at low lifetime risk, no specific surveillance will be proposed.

The Swedish family-cancer database: update, application to colorectal cancer and clinical relevance

The Swedish Family-Cancer Database has been used for almost 10 years in the study of familial risks at all common sites. In the present paper we describe some main features of version VI of this Database, assembled in 2004. This update included all Swedes born in 1932 and later (offspring) with their biological parents, a total of 10.5 million individuals. Cancer cases were retrieved from the Swedish Cancer Registry from 1958-2002, including over 1.2 million first and multiple primary cancers and in situ tumours. Compared to previous versions, only 6.0% of deceased offspring with a cancer diagnosis lack any parental information. We show one application of the Database in the study of familial risks in colorectal adenocarcinoma, with defined age-group and anatomic site specific analyses. Familial standardized incidence ratios (SIRs) were determined for offspring when parents or sibling were diagnosed with colon or rectal cancer. As a novel finding it was shown that risks for siblings were higher than those for offspring of affected parents. The excess risk was limited to colon cancer and particularly to right-sided colon cancer. The SIRs for colon cancer in age matched populations were 2.58 when parents were probands and 3.81 when siblings were probands; for right-sided colon cancer the SIRs were 3.66 and 7.53, respectively. Thus the familial excess (SIR-1.00) was more than two fold higher for right-sided colon cancer. Colon and rectal cancers appeared to be distinguished between high-penetrant and recessive conditions that only affect the colon, whereas low-penetrant familial effects are shared by the two sites. Epidemiological studies can be used to generate clinical estimates for familial risk, conditioned on numbers of affected family members and their ages of onset. Useful risk estimates have been developed for familial breast and prostate cancers. Reliable risk estimates for other cancers should also be seriously considered for routine clinical recommendations, because practically all cancers show a familial effect and the risks are high for some of the rare neoplasms. The implementation of a unified management plan for familial cancers at large will be a major challenge to the clinical genetic counselling community.

Familial risks for colorectal cancer show evidence on recessive inheritance

Recent molecular genetic data have become available on a recessive inheritance in colorectal cancer (CRC). We wanted to search for evidence for recessive inheritance from a population-based family data set, which is not sensitive to reporting or ascertainment bias. The nationwide Swedish Family-Cancer Database covered 10.3 million individuals whose invasive CRCs of adenocarcinoma histology were followed from 1991 to 2000. Age of the offspring and parental populations was limited to less than 69 years. Standardized incidence ratios (SIRs) were calculated for site-specific CRC in offspring whose parents or siblings were diagnosed with CRC. A total of 6,774 offspring were recorded with CRC, whose risk was 2.13 when a parent was diagnosed with CRC and it was 2.75 when a sibling was affected. The SIRs for right-sided colon cancer were 7.53 among siblings and 3.66 among offspring of affected parents, giving a 1.8-fold excess familial risk among siblings. Colon cancer among the 0- to 68-year-old population accounted for about 25% of all colon cancers. Examination of all cancers in family members of the affected siblings did not reveal large contribution by known syndromes, such as hereditary nonpolyposis colorectal cancer. The most likely explanation to the high risk of right-sided colon cancer among siblings is a recessive inheritance, which would account for 0.75% of all CRCs. Its high prevalence and predilection to right-sided colon suggest that only a small proportion of this familial aggregation could be due to MYH mutations.

Familial Risk for Colorectal Cancers Are Mainly Due to Heritable Causes

A family history is an identified risk factor for colorectal cancer (CRC). However, it is not known to what extent the risk is due to environmental or heritable genetic factors. We wanted to examine this question for familial CRC adenocarcinoma based on the nationwide Swedish Family-Cancer Database on 10.3 million individuals whose invasive cancers were followed up to year 2000. Standardized incidence ratios (SIRs) for offspring, siblings, and spouses were calculated based on 5-year age, sex, period (10-year bands), area (county), and socioeconomic status standardized rates. A significant risk was observed in the parent-offspring comparison among different subsites (left-sided and right-sided colon, rectum, and all CRC), the SIRs ranging from 1.74 to 1.84. When husbands were probands, the SIR in wives was 0.92 for colon cancer (left-sided 0.67 and right-sided 1.07), 0.98 for rectal cancer, and 0.96 for CRC. The risks for husbands when wives were probands were quite similar. None of the SIRs between spouses were significant, indicating lack of concordance between spouses that resided together for a minimum of 30 years. The risks between siblings were also increased particularly for cancer in the right-sided colon (SIR 6.89). The effect of shared childhood environmental effects were probed by analyzing the risks by age difference between the siblings. However, the risks were independent of the age difference. Data among spouses and siblings consistently point to the importance of heritable factors in familial CRC.

Family History and Environmental Risk Factors for Colon Cancer

Background: We analyzed the joint effect of environmental risk factors and family history of colorectal cancer on colon cancer. Methods: We used data from a case-control study conducted in northern Italy between 1992 and 1996 including 1225 cases with colon cancer and 4154 controls. We created a weighed risk factor score for the main environmental risk factors in this population (positive family history, high education, low occupational physical activity, high daily meal frequency, low intake of fiber, low intake of calcium, and low intake of β-carotene). Results: Compared with the reference category (subjects with no family history of colorectal cancer and in the lowest tertile of the risk factor score), the odds ratios of colon cancer were 2.27 [95% confidence interval (CI) = 1.89–2.73] for subjects without family history and in the highest environmental risk factor score, 3.20 (95% CI = 2.05–5.01) for those with family history and low risk factor score, and 7.08 (95% CI = 4.68–10.71) for those with family history and high risk factor score. The pattern of risk was similar for men and women and no meaningful differences emerged according to subsite within the colon. Conclusions: Family history of colorectal cancer interacts with environmental risk factors of colon cancer.

Revised Bethesda Guidelines for hereditary nonpolyposis colorectal cancer (Lynch syndrome) and microsatellite instability

Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is a common autosomal dominant syndrome characterized by early age at onset, neoplastic lesions, and microsatellite instability (MSI). Because cancers with MSI account for approximately 15% of all colorectal cancers and because of the need for a better understanding of the clinical and histologic manifestations of HNPCC, the National Cancer Institute hosted an international workshop on HNPCC in 1996, which led to the development of the Bethesda Guidelines for the identification of individuals with HNPCC who should be tested for MSI. To consider revision and improvement of the Bethesda Guidelines, another HNPCC workshop was held at the National Cancer Institute in Bethesda, MD, in 2002. In this commentary, we summarize the Workshop presentations on HNPCC and MSI testing; present the issues relating to the performance, sensitivity, and specificity of the Bethesda Guidelines; outline the revised Bethesda Guidelines for identifying individuals at risk for HNPCC; and recommend criteria for MSI testing.

Familial risks of cancer as a guide to gene identification and mode of inheritance

Occurrence of cancer in parents and offspring may be due to dominant causes, whereas cancer affecting only siblings may indicate a recessive causation. Systematic comparisons of mode of inheritance have not been available for most types of cancer. Using the Swedish Family-Cancer Database, standardized incidence ratios (SIR) were calculated for offspring whose parents or siblings were diagnosed with the same cancer. The degree of environmental causation was assessed by spouse correlation and by comparing risks among siblings of different ages. We identified reliable familial risks for all common neoplasms, SIRs ranging from 1.6 to 4.3 when only a parent was affected and up to 8.5 when only a sibling was effected. Risks between siblings were particularly high for renal cancer. Spouse correlation was found only for lung and stomach cancer, but the analysis of sibling risks by their age difference suggested that even for some other cancers environmental effects in childhood may contribute to familial aggregation. The results from these analysis suggest that familial cluster of cancer at most sites is heritable, caused by dominant effects; for renal cancer recessive effects may be most important.

Genetic epidemiology of cancer: From families to heritable genes

A reliable determination of familial risks for cancer is important for clinical counseling, prevention and understanding cancer etiology. Family-based gene identification efforts may be targeted if the risks are well characterized and the mode of inheritance is identified. Medically verified data on familial risks have not been available for all types of cancer but they have become available through the use of the nationwide Swedish Family-Cancer Database, which includes all Swedes born in 1932 and later with their parents, totaling over 10 million individuals. Over 150 publications have emanated from this source. The familial risks of cancer have been characterized for all main cancers and the contribution of environmental and heritable effects to the familial aggregation has been assessed. Furthermore, the mode of inheritance has been deduced by comparing risks from parental and sibling probands. Examples are shown on familial clustering of cancers, for which heritable susceptibility genes are yet unknown, such as squamous cell carcinoma of the skin, intestinal carcinoids, thyroid papillary tumors, brain astrocytomas and pituitary adenomas. Some common cancers, such as lung and kidney cancers, appear to show an early-onset recessive component because familial risks among siblings are much higher than those in families where parents are probands. Many of the cancer sites showing high familial risks lack guidelines for clinical counseling or action level. In conclusion, we recommend that any future gene identification efforts, either using linkage or association designs, devise their strategies based on data from family studies. Clinical genetic counseling would benefit from reviewing established familial risks on all main types of cancer.

Clinical characteristics and diagnosis of patients with hereditary nonpolyposis colorectal cancer

AIM: To study the clinical characteristics of hereditary nonpolyposis colorectal cancer (HNPCC) in the Chinese population and discuss the identification and management of the patients with HNPCC.

METHODS: A series of 140 patients with colorectal cancers (CRC) and HNPCC associated tumors from 30 families fulfilling the Amsterdam criteria were analyzed.

RESULTS: A total of 118 patients had CRC. Average age at diagnosis of the first CRC was 45.7 years, 56.8% and 23.4% of the first CRC were located proximal to the splenic flexure and in the rectum respectively. Twenty-three (19.5%) had synchronous and metachronous CRC. Twenty-seven patients were found to have extracolonic tumors. Gastric carcinoma was the most common tumor type in our series (44.4%).

CONCLUSION: The frequency of HNPCC was 2.6% in our series of patients. The main features are an excess of early onset with a propensity to involve the proximal colon, and high frequency of multiple foci. Management and surveillance for these patients should be different from sporadic CRC. Contrary to American and European reports, gastric cancer seems more frequent than endometrial cancer in Chinese. It is necessary to formulate a new HNPCC criterion for Chinese patients.

Familial risk of cancer: Data for clinical counseling and cancer genetics

Familial risks for cancer are important for clinical counseling and understanding cancer etiology. Medically verified data on familial risks have not been available for all types of cancer. The nationwide Swedish Family-Cancer Database includes all Swedes born in 1932 and later (0-to 68-year-old offspring) with their parents, totaling over 10.2 million individuals. Cancer cases were retrieved from the Swedish Cancer Registry up to year 2000. Standardized incidence ratios (SIR) and 95% confidence limits (CI) were calculated for age-specific familial risk in offspring by an exact proband status. The familial risks for offspring cancer were increased at 24/25 sites from concordant cancer in only the parent, at 20/21 sites from a sibling proband and at 12/12 sites from a parent and sibling proband. The highest SIRs by parent were for Hodgkin's disease (4.88) and testicular (4.26), non-medullary thyroid (3.26), ovarian (3.15) and esophageal (3.14) cancer and for multiple myeloma (3.33). When a sibling was affected, even prostate, renal, squamous cell skin, endocrine, gastric and lung cancer and leukemia showed SIRs in excess of 3.00. The highest cumulative risks were found for familial breast (5.5%) and prostate (4.2%) cancers. We identified reliable familial risks for 24 common neoplasms, most of which lack guidelines for clinical counseling or action level. If, for example, a familial SIR of 2.2 would be use as an action level, counseling would be needed for most cancers at some diagnostic age groups. The present data provide the basis for clinical counseling.

Familial risk of cancer by site and histopathology

Familial risks for histopathology-specific cancers have not been determined. We used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and 1 million tumors to calculate standardized incidence ratios (SIRs) for familial cancers of specific histology and morphology among 0- to 66-year-old offspring. We used histology codes for both offspring and parents, but because of the limited number of cases, the morphology-specific classification could be used only for offspring by all site-specific cancers in parents, resulting in inflated risk estimates. A number of novel findings emerged in the histopathology-specific analysis of familial risks, in addition to some known associations. Overall, specific histology showed an SIR of 2.07 for all cancers compared to an SIR of 2.00 for any histology. However, the small effect was due to breast and prostate cancers, which showed a negligible effect of specific histology. Familial risks of over 4.0 were found for serous papillary cystadenocarcinoma of the ovary, papillary thyroid cancer and low-grade astrocytoma. Familial risks of over 3.0 were found for signet-ring gastric cancer, various forms of ovarian cancer and squamous cell skin cancer. Also noteworthy were familial risks of hepatocellular carcinoma (2.48), pancreatic adenocarcinoma (1.92), large cell carcinoma and adenocarcinoma of the lung (2.29 and 2.18, respectively) and clear cell carcinoma of the kidney (2.73). Many of the findings were novel and could be revealed only by applying codes for specific histopathology. These data call for a closer description of familial aggregations and probing for the underlying genetic mechanisms.

Familial and second gastric carcinomas: a nationwide epidemiologic study from Sweden

BACKGROUND

Familial risks in gastric carcinoma have been assessed mainly through case-control studies based on reported but not medically verified carcinomas in family members. Reliable data on familial risks are needed for prevention and clinical decisions.

METHODS

The authors used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and more than 34,000 gastric carcinomas to calculate standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for gastric carcinoma in offspring, from birth to 66 years old, by carcinomas in family members. In addition, SIRs for second gastric carcinomas were analyzed.

RESULTS

Standardized incidence ratios for gastric carcinoma were 1.31 (95% CI, 0.97-1.70) and 1.47 (95% CI, 1.08-1.92) when a parent presented with gastric carcinoma or gastric adenocarcinoma, respectively. The risk was 1.59 (95% CI, 1.10-2.16) in offspring whose diagnosis was at ages older than 50 years. Offspring risk from parental corpus carcinoma was of borderline significance whereas that from cardia carcinoma was below unity. The sibling risk for gastric carcinoma was 3.16 (95% CI, 1.35-5.72) and 5.75 (95% CI, 2.07-11.26) when diagnosed before age 50. The population attributable proportion of familial gastric carcinoma was 0.45%. Risks for second gastric carcinomas were increased in men and women after esophageal and skin carcinomas, and after non-Hodgkin lymphoma.

CONCLUSIONS

The data suggest that environmental factors, perhaps Helicobacter pylori infections are the main reason for familial clustering of gastric carcinoma. The population attributable proportion of familial gastric carcinoma is much lower than that cited in the literature. The patterns of multiple carcinomas suggest that immunologic factors modulate susceptibility to gastric carcinoma.

Familial colorectal adenocarcinoma from the Swedish Family-Cancer Database

Familial risks for colorectal (CRC) adenocarcinoma were characterized from the Swedish Family-Cancer Database covering 9.6 million individuals, whose family relationships and cancers were obtained from registered sources, not sensitive to reporting or ascertainment bias. Cancer cases were retrieved from the Swedish Cancer Registry from years 1958-96. Standardized incidence ratios (SIRs) were calculated based on gender-, age-, period- and tumor type specific rates. A total of 4,794 and 67,925 CRCs were recorded in offspring and parents, respectively. For colon and rectal adenocarcinoma, the SIRs in offspring were 2.28 and 1.68 by parental CRC adenocarcinoma, giving attributable proportions of 6.45 and 3.31%, respectively. The SIR of CRC was over 10 when both offspring and parents were diagnosed at a young age. The risk for parental CRC adenocarcinoma was over 100 when 2 or more children were affected. The risk in siblings was also very high when a parent was affected. The familial cancer sites that associated with CRC were those typical of hereditary nonpolyposis colorectal cancer (HNPCC). This is the largest study published on familial CRC and the only one reporting specifically on adenocarcinoma. The data suggest that HNPCC is the largest single disease entity among CRCs, probably accounting for less than 50% of familial CRC. Other familial components appear heterogeneous, characterized by incomplete penetrance, recessive mode of inheritance and few associated tumor sites.