Characterization of hereditary nonpolyposis colorectal cancer families from a population-based series of cases.

BACKGROUND: The incidence of hereditary nonpolyposis colon cancer (HNPCC) in the general population is not well defined because of the lack of large population-based studies. We characterized the incidence of HNPCC in a large, population-based cohort of colorectal cancer probands and analyzed the location of colorectal tumors. METHODS: Of the participating 1134 probands from three counties in Southern California, 907 had a negative family history of colorectal cancer and 227 had a positive family history of colorectal cancer. In addition, 11 referral case subjects with HNPCC were used to study mutation frequencies in two mismatch repair genes (MSH2 and MLH1) and microsatellite instability. All statistical tests were two-sided. RESULTS: Among the probands diagnosed in Orange County during 1994 (population-based sample, all ages), five were consistent with the Amsterdam criteria for HNPCC (0.9%; 95% confidence interval [CI] = 0. 3%-2.1%). Among probands diagnosed at less than 65 years of age-from the wider three-county area and a longer time span-16 (2.1%; 95% CI = 1.2%-3.4%) had a clinical history consistent with the Amsterdam criteria for HNPCC. Five (approximately 45%) of 11 of the referral HNPCC case subjects had a mutation in MSH2 or MLH1 and also showed microsatellite instability. The family members of case subjects with mutations tended to show an earlier age at diagnosis of HNPCC and more multiple primary cancers than those of case subjects without detectable mutations. Many of the known characteristics of HNPCC, including the presence of ureteral and endometrial cancers, were seen in both sets of families. The previously reported proximal location of colorectal tumors in HNPCC kindreds was not seen in the population-based dataset but was similar to the location reported in the referral cases. CONCLUSIONS: On the basis of our data, we believe that the prevalence of HNPCC in the general population is likely to be closer to 1% than to 5%. Furthermore, our study suggests that some previously reported characteristics of HNPCC, such as the proximal location of tumors in the syndrome, may not always hold true in a population-based sample.

Cancer risk estimates for family members of a population-based family registry for breast and ovarian cancer.

Population-based breast and ovarian cancer family registries can facilitate studies to evaluate genetic and environmental factors in the etiology of these malignancies. The purpose of this study is to describe what is, as far as we know, the first population-based breast and ovarian cancer family registry and to estimate breast and ovarian cancer risk in relatives of breast and ovarian cancer probands. Population-based consecutive incident cases of breast and ovarian cancer were invited to participate in the University of California, Irvine breast and ovarian family registry. In this study, we report data on 1567 breast cancer and 328 ovarian cancer probands. The operational components of this family registry include enrollment of probands, family history interviewing, confidentiality, pathology, verification and review, biospecimen bank, statistical/genetic analysis, and special studies on positional cloning of known genes. All of the components are tracked through the University of California, Irvine Genetic Research Information System. In non-Hispanic-white breast cancer probands, relative risk (RR) of breast cancer in mothers and sisters is significantly elevated [RR = 1.7 and 95% confidence interval (CI) = 1.4-2.0 and RR = 2.8 and 95% CI = 2.3-3.3, respectively]. In families of ovarian cancer probands, mothers are at increased risk of ovarian cancer (RR = 4.6; 95% CI, 2.1-8.7). RR of breast cancer in mothers of Hispanic breast cancer probands is significantly elevated (RR = 4.9; 95% CI, 2.6-8.5). No elevation of breast or ovarian cancer risk was observed among relatives of Asian probands. In general, there is a decrease in RR among mothers and sisters with increase in age of onset of probands. In second-degree relatives and first cousins, the breast cancer hazards ratios increase with increase in the number of affected first-degree relatives and decrease with increase in age at onset of the proband.

Characteristics of BRCA1 mutations in a population-based case series of breast and ovarian cancer.

Breast and ovarian cancers account for approximately 210000 newly diagnosed cases per year. More than half a million American women are estimated to be carriers of a breast cancer susceptibility gene. The purpose of this study was to assess the association of characteristics such as, age at diagnosis, race/ethnicity and family history of cancer with inherited BRCA1 mutations in a population-based sample of breast and ovarian cancer cases. No selection was made by race, age at diagnosis or positive family history of breast or ovarian cancer. The population under study was all breast cancer cases diagnosed in Orange County, CA, during the 1-year period beginning 1 March 1994 and all ovarian cancer cases diagnosed in Orange County during the 2-year period beginning 1 March 1994. This report focuses on the first consecutively ascertained 802 participating probands enrolled in the study, of which 9 were male breast cancer probands, 673 were female breast cancer probands and 120 were ovarian cancer probands. We observed 11 BRCA1 mutations or 1.6% (95% CI: 0.8-2.9) among the 673 female breast cancer probands and 4 BRCA1 mutations or 3.3% (95% CI: 0.8-8. 3) among the 120 ovarian cancer probands. No BRCA1 mutations were identified among the 98 non-white breast and ovarian cancer probands. The prevalence of BRCA1 mutations in non-Hispanic-white breast cancer cases below the age of 50 years was 2%. Positive family history of breast or ovarian cancers was significantly associated with BRCA1 mutation status among breast cancer probands. Similarly, positive family history of breast or ovarian cancer was significantly associated with BRCA1 mutation status among the ovarian cancer probands. In summary, we present results on the prevalence of BRCA1 mutations in a significantly larger sample of population-based breast and ovarian cancer cases than previously reported. The results indicate that, using a conservative approach to targeted genotyping of BRCA1, the frequency of mutations was consistent with those reported using similar methods of population-based case ascertainment.

Validation of family history of breast cancer and identification of the BRCA1 and other syndromes using a population-based cancer registry.

A major risk factor for breast cancer is family history of the disease in first-degree relatives. This study evaluates the validity of family history information on breast cancer in mothers and sisters of breast cancer probands from the cancer registry (CR) compared to personal interviews (PI) of 359 consecutive population-based cases of breast cancer. Breast cancer is seen in mothers of 14% of probands by CR compared to 12% by PI. Further, 13% of probands have a sister with breast cancer using CR compared to 12% by PI. Using PI as the standard, the sensitivity of the CR family history data in mothers is 92% and the specificity is 99%, while in sisters they are 88% and 99%, respectively. These estimates were calculated on cases where family history information is available in the CR. Sensitivity and specificity are recalculated, recording an "error" whenever family history information is not available, and they are 75% and 68%, respectively, for mothers and 72% and 70%, respectively, for sisters. Estimates of proband-mother and proband-sisters familial breast cancer from CR and PI are sufficiently similar to warrant the use of CR family history data in studies of genetic epidemiology. The family phenotype consistent with the BRCA1 syndrome was found in four (1.1%) probands, all below age 50 years, while for BRCA2 there were five (1.4%) probands, three below age 50 years and two 50 years or older. Site-specific familial breast cancer was found in 23 (6.4%) probands. Population-based multiple-case breast cancer families can rapidly be identified through CR. These families can make substantial contributions to the study of genetic and environmental etiology of the disease as well as benefit from preventive and therapeutic efforts. As new knowledge and tools in molecular genetics become available, there is an urgent need for large population-based registries of families at high risk for cancer.

Hormone replacement therapy in breast cancer survivors: a cohort study.

OBJECTIVE: Our purpose was to measure any adverse effect (if one exists) of hormone replacement therapy administered to breast cancer survivors. STUDY DESIGN: Forty-one patients from a group of 77 patients who received hormone replacement therapy after therapy for breast cancer were matched with 82 comparison patients not receiving hormone replacement therapy. Both groups were taken from the same population on the basis of cancer registry of the Cancer Surveillance Program of Orange County and were compared with regard to survival results. RESULTS: An analysis of survival time and disease-free time revealed no statistically significant difference between the two groups. CONCLUSIONS: No obvious adverse effect of hormone replacement therapy could be shown in this pilot study. A case is made for a prospective randomized trial.

Germline BRCA1 alterations in a population-based series of ovarian cancer cases.

The objective of this study was to provide more accurate frequency estimates of breast cancer susceptibility gene 1 ( BRCA1 ) germline alterations in the ovarian cancer population. To achieve this, we determined the prevalence of BRCA1 alterations in a population-based series of consecutive ovarian cancer cases. This is the first population-based ovarian cancer study reporting BRCA1 alterations derived from a comprehensive screen of the entire coding region. One hundred and seven ovarian cancer cases were analyzed for BRCA1 alterations using the RNase mismatch cleavage assay followed by direct sequencing. Two truncating mutations, 962del4 and 3600del11, were identified. Both patients had a family history of breast or ovarian cancer. Several novel as well as previously reported uncharacterized variants were also identified, some of which were associated with a family history of cancer. The frequency distribution of common polymorphisms was determined in the 91 Caucasian cancer cases in this series and 24 sister controls using allele-specific amplification. The rare form of the Q356R polymorphism was significantly ( P = 0.03) associated with a family history of ovarian cancer, suggesting that this polymorphism may influence ovarian cancer risk. In summary, our data suggest a role for some uncharacterized variants and rare forms of polymorphisms in determining ovarian cancer risk, and highlight the necessity to screen for missense alterations as well as truncating mutations in this population.