Kevin Sweet

Highly penetrant hereditary cancer syndromes

The past two decades have brought many important advances in our understanding of the hereditary susceptibility to cancer. Approximately 5–10% of all cancers are inherited, the majority in an autosomal dominant manner with incomplete penetrance. While this is a small fraction of the overall cancer burden worldwide, the molecular genetic discoveries that have resulted from the study of families with heritable cancer have not only changed the way these families are counselled and managed, but have shed light on molecular regulatory pathways important in sporadic tumour development as well. In this review, we consider 10 of the more highly penetrant cancer syndromes, with emphasis on those predisposing to breast, colon, and/or endocrine neoplasia. We discuss the prevalence, penetrance, and tumour spectrum associated with these syndromes, as well as their underlying genetic defects.

Identification and Referral of Families at High Risk for Cancer Susceptibility

PURPOSE Obtainment of family history and accurate assessment is essential for the identification of families at risk for hereditary cancer. Our study compared the extent to which the family cancer history in the physician medical record reflected that entered by patients directly into a touch-screen family history computer program. PATIENTS AND METHODS The study cohort consisted of 362 patients seen at a comprehensive cancer center ambulatory clinic over a 1-year period who voluntarily used the computer program and were a mixture of new and return patients. The computer entry was assessed by genetics staff and then compared with the medical record for corroboration of family history information and appropriate physician risk assessment. RESULTS Family history information from the medical record was available for comparison to the computer entry in 69%. It was most often completed on new patients only and not routinely updated. Of the 362 computer entries, 101 were assigned to a high-risk category. Evidence in the records confirmed 69 high-risk individuals. Documentation of physician risk assessment (ie, notation of significant family cancer history or hereditary risk) was found in only 14 of the high-risk charts. Only seven high-risk individuals (6.9%) had evidence of referral for genetic consultation. CONCLUSION This study demonstrates the need to collect family history information on all new and established patients in order to perform adequate cancer risk assessment. The lack of identification of patients at highest risk seems to be directly correlated with insufficient data collection, risk assessment, and documentation by medical staff.

Referral for cancer genetics consultation: a review and compilation of risk assessment criteria

Background: There have been many papers on the diagnostic criteria for specific hereditary cancer susceptibility syndromes and the likelihood that an individual has a germline mutation in one of the various cancer susceptibility genes. To assist health care professionals in deciding when a cancer genetics consultation is appropriate, available reports were critically reviewed in order to develop a single set of risk assessment criteria. Methods: The criteria were based on a comprehensive review of publications describing diagnostic criteria for hereditary cancer syndromes and risk to first degree relatives of cancer patients. Priority was given to diagnostic criteria from consensus statements (for example, those from the National Comprehensive Cancer Network). Expert opinion from study personnel was then used to adopt a single set of criteria from other publications whenever guidelines differed. Results: Based on family history, a set of criteria was developed to identify patients at risk for a hereditary cancer susceptibility syndrome, patients with moderate risk who might benefit from increased cancer surveillance, and patients who are at average risk. The criteria were applied to 4360 individuals who provided their cancer family history between July 1999 and April 2002, using a touch screen computer system in the lobby of a comprehensive cancer centre. They categorised an acceptable number of users into each risk level: 14.9% high risk, 13.7% moderate risk, and 59.6% average risk; 11.8% provided insufficient information for risk assessment. Conclusions: These criteria should improve ease of referral and promote consistency across centres when evaluating patients for referral to cancer genetics specialists.

Family History of Cancer and Cancer Risks in Women with BRCA1 or BRCA2 Mutations

Women who carry a deleterious mutation in BRCA1 or BRCA2 have high lifetime risks of breast and ovarian cancers. However, the influence of a family history of these cancers on these risks in women with BRCA mutations is unclear. We calculated cancer incidence rates for a multinational cohort comprising 3011 women with BRCA1 or BRCA2 mutations who were followed up for a mean of 3.9 years, during which time 243 incident breast or ovarian cancers were recorded. The 10-year cumulative risks of breast cancer were 18.1% (95% confidence interval [CI] = 13.3% to 22.8%) for women with a BRCA1 mutation and 15.2% (95% CI = 9.1% to 21.2%) for women with a BRCA2 mutation. Among women with a BRCA1 mutation, the risk of breast cancer increased by 1.2-fold for each first-degree relative with breast cancer before age 50 years (hazard ratio [HR] = 1.21; 95% confidence interval [CI] = 0.94 to 1.57) and the risk of ovarian cancer increased by 1.6 fold for each first- or second-degree relative with ovarian cancer (HR = 1.61; 95% CI = 1.21 to 2.14). Among women with a BRCA2 mutation, the risk of breast cancer increased by 1.7-fold for each first-degree relative younger than 50 years with breast cancer (HR = 1.67; 95% CI = 1.04 to 2.07).

Clinically Applicable Models to Characterize BRCA1 and BRCA2 Variants of Uncertain Significance

PURPOSE Twenty percent of individuals with a strong family and/or personal history of breast and ovarian cancer carry a deleterious mutation in BRCA1 or BRCA2. Identification of mutations in these genes is extremely beneficial for patients pursuing risk reduction strategies. Approximately 7% of individuals who have genetic testing of BRCA1 and BRCA2 carry a variant of uncertain significance (VUS), making clinical management less certain. The majority of identified VUS occur only in one to two individuals; these variants are not able to be classified using current classification models with segregation analysis components. METHODS To develop a clinically applicable method that can predict the pathogenicity of VUS that does not require familial information or segregation analysis, we identified characteristics of breast or ovarian tumors that distinguished sporadic tumors from tumors with BRCA1 or BRCA2 mutations. Study participants included individuals with known deleterious mutations in BRCA1 or BRCA2 and individuals with classified or unclassified BRCA variants. RESULTS We applied the models to 57 tumors with 43 different deleterious BRCA mutations and 57 tumors with 54 unique classified and unclassified BRCA variants. Of the 33 previously unclassified VUS studied, we found evidence of neutrality for 21. CONCLUSION Our models showed 98% sensitivity and 76% specificity for predicting classified DNA changes. We classified 64% of unknown variants as neutral. Classification of VUS as neutral will have immediate benefit for those individuals and their family members. These models are adaptable for the clinic and will be useful for individuals with limited available family history.

Cancer Risks for Relatives of Patients With Serrated Polyposis

OBJECTIVES:Serrated polyposis (hyperplastic polyposis) is characterized by multiple polyps with serrated architecture in the colorectum. Although patients with serrated polyposis are known to be at increased risk of colorectal cancer (CRC) and possibly extracolonic cancers, cancer risk for their relatives has not been widely explored. The aim of this study was to estimate the risks of CRC and extracolonic cancers for relatives of patients with serrated polyposis.METHODS:A cohort of the 1,639 first- and second-degree relatives of 100 index patients with serrated polyposis recruited regardless of a family history of polyps or cancer from genetic clinics in Australia, New Zealand, Canada, and the USA, were retrospectively analyzed to estimate the country-, age-, and sex-specific standardized incidence ratios (SIRs) for relatives compared with the general population.RESULTS:A total of 102 CRCs were observed in first- and second-relatives (SIR 2.25, 95% confidence interval (CI) 1.75–2.93; P<0.001), with 54 in first-degree relatives (SIR 5.16, 95% CI 3.70–7.30; P<0.001) and 48 in second-degree relatives (SIR 1.38, 95% CI 1.01–1.91; P=0.04). Six pancreatic cancers were observed in first-degree relatives (SIR 3.64, 95% CI 1.70–9.21; P=0.003). There was no statistical evidence of increased risk for cancer of the stomach, brain, breast, or prostate.CONCLUSIONS:Our finding that relatives of serrated polyposis patients are at significantly increased risk of colorectal and pancreatic cancer adds to the accumulating evidence that serrated polyposis has an inherited component.

Variability in organ-specific EGFR mutational spectra in tumour epithelium and stroma may be the biological basis for differential responses to tyrosine kinase inhibitors

Organ-specific differences in epidermal growth factor receptor (EGFR) mutational spectra and frequencies were found in lung cancer and sporadic and BRCA 1/2-related breast cancers. Additionally, we found a high frequency of EGFR mutations in the tumour stroma of these invasive breast carcinomas. Those organ-specific mutational spectra and potential targets in the cancer-associated stroma might influence the efficacy of TKI therapy.

Phenotype and polyp landscape in serrated polyposis syndrome: a series of 100 patients from genetics clinics.

Serrated polyposis syndrome (SPS), also known as hyperplastic polyposis, is a syndrome of unknown genetic basis defined by the occurrence of multiple serrated polyps in the large intestine and associated with an increased risk of colorectal cancer (CRC). There are a variety of SPS presentations, which may encompass a continuum of phenotypes modified by environmental and genetic factors. To explore the phenotype of SPS, we recorded the histologic and molecular characteristics of multiple colorectal polyps in patients with SPS recruited between 2000 and 2010 from genetics clinics in Australia, New Zealand, Canada, and the United States. Three specialist gastrointestinal pathologists reviewed the polyps, which they classified into conventional adenomas or serrated polyps, with various subtypes, according to the current World Health Organization criteria. Mutations in BRAF and KRAS and mismatch repair protein expression were determined in a subset of polyps. A total of 100 patients were selected for the study, of whom 58 were female and 42 were male. The total polyp count per patient ranged from 6 to 150 (median 30). The vast majority of patients (89%) had polyposis affecting the entire large intestine. From this cohort, 406 polyps were reviewed. Most of the polyps (83%) were serrated polyps: microvesicular hyperplastic polyps (HP) (n=156), goblet cell HP (n=25), sessile serrated adenoma/polyps (SSA/P) (n=110), SSA/P with cytologic dysplasia (n=28), and traditional serrated adenomas (n=18). A further 69 polyps were conventional adenomas. BRAF mutation was mainly detected in SSA/P with dysplasia (95%), SSA/P (85%), microvesicular HP (76%), and traditional serrated adenoma (54%), whereas KRAS mutation was present mainly in goblet cell HP (50%) and in tubulovillous adenoma (45%). Four of 6 SSA/Ps with high-grade dysplasia showed loss of MLH1/PMS2 expression. CRC was diagnosed in 39 patients who were more often found to have a conventional adenoma compared with patients without CRC (P=0.003). Patients with SPS referred to genetics clinics had a pancolonic disease with a high polyp burden and a high rate of BRAF mutation. The occurrence of CRC was associated with the presence of conventional adenoma.

Risk Factors for Colorectal Cancer in Patients with Multiple Serrated Polyps: A Cross-Sectional Case Series from Genetics Clinics

Background Patients with multiple serrated polyps are at an increased risk for developing colorectal cancer (CRC). Recent reports have linked cigarette smoking with the subset of CRC that develops from serrated polyps. The aim of this work therefore was to investigate the association between smoking and the risk of CRC in high-risk genetics clinic patients presenting with multiple serrated polyps. Methods and Findings We identified 151 Caucasian individuals with multiple serrated polyps including at least 5 outside the rectum, and classified patients into non-smokers, current or former smokers at the time of initial diagnosis of polyposis. Cases were individuals with multiple serrated polyps who presented with CRC. Controls were individuals with multiple serrated polyps and no CRC. Multivariate logistic regression was performed to estimate associations between smoking and CRC with adjustment for age at first presentation, sex and co-existing traditional adenomas, a feature that has been consistently linked with CRC risk in patients with multiple serrated polyps. CRC was present in 56 (37%) individuals at presentation. Patients with at least one adenoma were 4 times more likely to present with CRC compared with patients without adenomas (OR = 4.09; 95%CI 1.27 to 13.14; P = 0.02). For females, the odds of CRC decreased by 90% in current smokers as compared to never smokers (OR = 0.10; 95%CI 0.02 to 0.47; P = 0.004) after adjusting for age and adenomas. For males, there was no relationship between current smoking and CRC. There was no statistical evidence of an association between former smoking and CRC for both sexes. Conclusion A decreased odds for CRC was identified in females with multiple serrated polyps who currently smoke, independent of age and the presence of a traditional adenoma. Investigations into the biological basis for these observations could lead to non-smoking-related therapies being developed to decrease the risk of CRC and colectomy in these patients.

Methylation not a frequent “second hit” in tumors with germline BRCA mutations

Mutations in tumor suppressor genes BRCA1 and BRCA2 confer an increased lifetime risk of breast and ovarian cancer. Loss of heterozygosity (LOH) of the wildtype allele has been observed in ~80% of tumors from BRCA1 carriers and 70% of tumors from BRCA2 carriers and accounts for the majority of the “second-hits” occurring in BRCA-related tumors. Few sporadic tumors have been reported to have mutations in BRCA. Some sporadic tumors do show LOH of BRCA1 and BRCA2. BRCA1 promoter methylation has also been observed in sporadic ovarian and breast tumors; however, BRCA2 promoter methylation has not been reported in sporadic tumors. The relationship between BRCA LOH and BRCA promoter methylation has not been well characterized in tumors from BRCA germline mutation carriers. The goal of this study was to determine if BRCA1 and BRCA2 promoter hypermethylation serves as a “second-hit” in tumors from mutation carriers that do not show LOH. We studied 38 tumors from BRCA1 carriers and 23 tumors from BRCA2 carriers for LOH. To determine if BRCA1 and BRCA2 promoter hypermethylation serves as a “second-hit” in tumors with germline mutations, we tested 15 tumors lacking LOH and nine tumors with LOH for BRCA1 or BRCA2 promoter methylation. We identified seven BRCA1 tumors and nine BRCA2 tumors lacking LOH. Of these, only one tumor with a BRCA2 mutation showed promoter methylation. These data indicate that promoter methylation is a not a frequent “second-hit” in tumors from BRCA1 or BRCA2 carriers.