Mice heterozygous for mutation in Atm, the gene involved in ataxia-telangiectasia, have heightened susceptibility to cancer.

Ataxia-telangiectasia is characterized by radiosensitivity, genome instability and predisposition to cancer. Heterozygous carriers of ATM, the gene defective in ataxia-telangiectasia, have a higher than normal risk of developing breast and other cancers. We demonstrate here that Atm 'knock-in' (Atm-Delta SRI) heterozygous mice harboring an in-frame deletion corresponding to the human 7636del9 mutation show an increased susceptibility to developing tumors. In contrast, no tumors are observed in Atm knockout (Atm(+/-)) heterozygous mice. In parallel, we report the appearance of tumors in 6 humans from 12 families who are heterozygous for the 7636del9 mutation. Expression of ATM cDNA containing the 7636del9 mutation had a dominant-negative effect in control cells, inhibiting radiation-induced ATM kinase activity in vivo and in vitro. This reduces the survival of these cells after radiation exposure and enhances the level of radiation-induced chromosomal aberrations. These results show for the first time that mouse carriers of a mutated Atm that are capable of expressing Atm have a higher risk of cancer. This finding provides further support for cancer predisposition in human ataxia-telangiectasia carriers.

Early menstrual characteristics associated with subsequent diagnosis of endometriosis.

OBJECTIVE: The aim of this study was to investigate the association between early menstrual characteristics, before symptom onset, and later diagnosis of endometriosis. STUDY DESIGN: This was a case-control study of 268 Australian women with surgically confirmed moderate-to-severe endometriosis (cases) and 244 women without endometriosis (controls). Early menstrual cycle characteristics, before age at symptom onset, were analyzed. RESULTS: Menarche after age 14 years was strongly and inversely associated with endometriosis (odds ratio, 0.3; 95% confidence interval, 0.1-0.6). A history of dysmenorrhea was associated with subsequent endometriosis (odds ratio, 2.6; 95% confidence interval, 1.1-6.2). Despite a suggestive trend, shorter menstrual cycle length was not associated with endometriosis. Duration of natural menstruation and heaviness of flow were not associated with subsequent risk of endometriosis; neither was the reported type of sanitary protection used nor history of sexual intercourse during menstruation. CONCLUSION: There is a decreased risk of endometriosis with late age at menarche and an increased risk in women who report an early history of dysmenorrhea.

Clinical outcomes associated with bevacizumab-containing treatment of metastatic colorectal cancer: the BRiTE observational cohort study.

BACKGROUND: The Bevacizumab Regimens' Investigation of Treatment Effects (BRiTE) study is a prospective, observational cohort study designed to elucidate safety and effectiveness outcomes associated with bevacizumab combined with chemotherapy as used in clinical practice for first-line treatment of metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: Baseline characteristics, prespecified bevacizumab-related adverse events, and effectiveness data were collected from 1,953 mCRC patients who were receiving first-line treatment including bevacizumab at 248 U.S. sites. RESULTS: At database lock, the median follow-up was 20.1 months. At baseline, 46% of patients were aged >or=65 years and 49% had an Eastern Cooperative Oncology Group performance status score >or=1. Fluorouracil, leucovorin, and oxaliplatin was the most common first-line chemotherapy regimen (56%). Overall rates of bevacizumab-related adverse events in the BRiTE study, such as gastrointestinal perforation (1.9%), arterial thromboembolic events (2%), grade 3-4 bleeding (2.2%), and de novo hypertension requiring medication (22%), were consistent with those reported in randomized clinical trials (RCTs) of bevacizumab in first-line mCRC treatment. The median progression-free survival (PFS) and overall survival (OS) times were 9.9 (95% confidence interval [CI], 9.5-10.3) months and 22.9 (95% CI, 21.9-24.4) months, respectively. CONCLUSION: The median PFS and OS durations and safety profile of bevacizumab in the BRiTE study were similar to those in RCTs of bevacizumab plus chemotherapy in first-line mCRC patients. The observations from the BRiTE study complement and expand upon RCT data, providing clinical information in a large cohort of bevacizumab-treated patients and subgroups such as the elderly.

Incomplete pregnancy and risk of ovarian cancer: results from two Australian case-control studies and systematic review.

Although full-term pregnancies reduce the risk of ovarian cancer, it has not been conclusively established whether incomplete pregnancies also influence risk. We investigated the relationship between a history of incomplete pregnancy and incident epithelial ovarian cancer among over 4,500 women who participated in two large Australian population-based case-control studies in 1990-1993 and 2002-2005. They provided responses to detailed questions about their reproductive histories and other personal factors. Summary odds ratios (OR) and confidence intervals (CI) derived for each study using the same covariates were aggregated. We found no significant associations between the number of incomplete pregnancies and ovarian cancer, for parous (OR = 0.98, 95% CI: 0.89, 1.08) or nulliparous (OR = 1.06, 95% CI: 0.75, 1.48) women, nor for the number of spontaneous or induced abortions and ovarian cancer for parous women (OR = 0.95, 95% CI 0.82, 1.09; OR = 1.08, 95% CI: 0.86, 1.36) or nulliparous women (OR = 1.2, 95% CI: 0.6, 2.4; OR = 0.8, 95% CI: 0.47, 1.38), respectively. A systematic review of 37 previous studies of the topic confirmed our findings that a history of incomplete pregnancy does not influence a woman's risk of epithelial ovarian cancer.

Assessment of hepatic steatosis: comparison of quantitative and semiquantitative methods in 108 liver biopsies.

BACKGROUND: There is growing interest in the role of hepatic steatosis in liver injury. The current standard for steatosis assessment is histological grading, although there is variability in the scoring systems used. AIMS: The aim of this study was to compare steatosis assessment by image analysis and histological grading. METHODS: Three methods were used to measure steatosis: histological grading (from 0 to 4); estimation of the percentage of hepatocytes (to nearest 5%) with steatosis; and computer-assisted image analysis. Image analysis was performed on multiple fields for each biopsy with image pro plus 4.5, with steatotic droplets identified on the basis of shape, colour and size. Computer-selected objects were reviewed to ensure that these were steatotic droplets. The predictive accuracy of the three techniques was assessed using measures of obesity and insulin resistance (homeostasis model assessment) as the outcome variables. RESULTS: There was a strong correlation between the results of image analysis and histological grade (r(s)=0.89, P<0.01), and estimated per cent steatosis (r(s)=0.93, P<0.01). The variability in the area of steatosis calculated by image analysis in different fields of a biopsy correlated with the total steatosis area (r(s)=0.93, P<0.01). CONCLUSIONS: Image analysis did not offer any additional predictive value when the association between degree of obesity or insulin resistance was correlated with the different methods of assessing steatosis. Image analysis allows measurement of area of steatosis in liver biopsy material and generates a continuous variable that facilitates statistical analysis. These aspects may prove beneficial in research settings.

Body size and risk of epithelial ovarian and related cancers: a population-based case-control study.

Different subtypes of ovarian cancer appear to have different causes; however, the association between body mass index (BMI) and the different subtypes is unclear. We examined the associations between body-mass index (BMI) and weight gain and risk of the different histological subtypes of epithelial ovarian cancer in a case-control study in Australia. Cases aged 18-79 with a new diagnosis of invasive epithelial ovarian cancer (n = 1,269) or borderline tumor (n = 311) were identified through a network of clinics and cancer registries throughout Australia. Controls (n = 1,509) were selected from the Electoral Roll. Height and weight (1 year previously, at age 20 and maximum weight) and other risk factor information were ascertained via a self-administered questionnaire. Obesity was positively associated with clear cell tumors (Odds Ratio 2.3; 95% confidence interval 1.2-4.2) but not invasive endometrioid or mucinous tumors. Although there was no association with invasive serous tumors overall (0.9; 0.7-1.2), we did see an increased risk of serous peritoneal tumors (2.9; 1.7-4.9), but not of serous tumors of the ovary and fallopian tube. Of the borderline subtypes, obesity was positively associated with serous (1.8; 1.1-2.8) but not mucinous tumors (1.1; 0.7-1.7). Overweight was not associated with any subtype overall. There was no association with BMI at age 20, or weight gain for any of the histological subtypes. These results add to the current evidence that obesity increases a woman's risk of developing distinct histological subtypes of ovarian cancer.

Population health and clinical data linkage: the importance of a population registry.

OBJECTIVE: The Australian National Collaborative Research Infrastructure Strategy supports development of a national research capability in population health and clinical data linkage. This paper illustrates the importance of incorporating a population registry within such a system using an example provided by the Manitoba Injury Outcome Study (MIOS) that quantified the long-term burden of mortality attributable to injury in working-age adults. METHODS: MIOS is a population-based matched cohort study that used administrative health data from Manitoba, Canada. An inception cohort of injured cases (ICD-9-CM 800-995) aged 18-64 years was identified from all Manitoba hospital admissions between 1988 and 1991. A matched non-injured comparison group was randomly selected from the total provincial population using the Manitoba Population Registry. Mortality outcomes were obtained by linking the two cohorts with the deaths data over 10 years. Mortality rate ratios (MRRs) were calculated to compare the injured and non-injured cohorts. RESULTS: A total of 21,032 matched pairs were identified. Using the population registry, the 10-year adjusted all-cause MRR comparing injured and non-injured cohort was 1.80 (95% CI 1.65-1.98). Without the registry, the unadjusted standardised morality ratio was 2.76 (95% CI 2.52-3.02). CONCLUSIONS: The effect of injury on mortality outcomes was over-estimated using only the injured cases, without use of the population registry. Use of the population registry enabled the selection of a matched non-injured group for comparison purposes, ensured comprehensive follow-up of almost all participants, and provided more accurate estimates of exposure time, incidence of mortality and relative risk.

Screening for hemochromatosis in asymptomatic subjects with or without a family history.

BACKGROUND: Hemochromatosis in white subjects is mostly due to homozygosity for the common C282Y substitution in HFE. Although clinical symptoms are preventable by early detection of the genetic predisposition and prophylactic treatment, population screening is not currently advocated because of the discrepancy between the common mutation prevalence and apparently lower frequency of clinical disease. This study compared screening for hemochromatosis in subjects with or without a family history. METHODS: We assessed disease expression by clinical evaluation and liver biopsy in 672 essentially asymptomatic C282Y homozygous subjects identified by either family screening or health checks. We also observed a subgroup of untreated homozygotes with normal serum ferritin levels for up to 24 years. RESULTS: Prevalence of hepatic iron overload and fibrosis were comparable between the 2 groups. Disease-related conditions were more common in male subjects identified by health checks, but they were older. Hepatic iron overload (grades 2-4) was present in 56% and 34.5% of male and female subjects, respectively; hepatic fibrosis (stages 2-4) in 18.4% and 5.4%; and cirrhosis in 5.6% and 1.9%. Hepatic fibrosis and cirrhosis correlated significantly with the hepatic iron concentration, and except in cases of cirrhosis, there was a 7.5-fold reduction in the mean fibrosis score after phlebotomy. All subjects with cirrhosis were asymptomatic. CONCLUSIONS: Screening for hemochromatosis in apparently healthy subjects homozygous for the C282Y mutation with or without a family history reveals comparable levels of hepatic iron overload and disease. Significant hepatic fibrosis is frequently found in asymptomatic subjects with hemochromatosis and, except when cirrhosis is present, is reversed by iron removal.

Population attributable risk of breast cancer in white women associated with immediately modifiable risk factors.

BACKGROUND: Estrogen/progestin replacement therapy (EPRT), alcohol consumption, physical activity, and breast-feeding duration differ from other factors associated with breast cancer in being immediately modifiable by the individual, thereby representing attractive targets for future breast cancer prevention efforts. To justify such efforts, it is vital to quantify the potential population-level impacts on breast cancer considering population variations in behavior prevalence, risk estimate, and baseline incidence. METHODS: For each of these four factors, we calculated population attributable risk percents (PARs) using population-based survey (2001) and cancer registry data (1998-2002) for 41 subpopulations of white, non-Hispanic California women aged 40-79 years, and ranges of relative risk (RR) estimates from the literature. RESULTS: Using a single RR estimate, subpopulation PARs ranged from 2.5% to 5.6% for hormone use, from 0.0% to 6.1% for recent consumption of > or = 2 alcoholic drinks daily, and 4.6% to 11.0% for physical inactivity. Using a range of RR estimates, PARs were 2-11% for EPRT use, 1-20% for alcohol consumption and 2-15% for physical inactivity. Subpopulation data were unavailable for breastfeeding, but PARs using published RR estimates ranged from 2% to 11% for lifetime breastfeeding > or = 31 months. Thus, of 13,019 breast cancers diagnosed annually in California, as many as 1,432 attributable to EPRT use, 2,604 attributable to alcohol consumption, 1,953 attributable to physical inactivity, and 1,432 attributable to never breastfeeding might be avoidable. CONCLUSION: The relatively feasible lifestyle changes of discontinuing EPRT use, reducing alcohol consumption, increasing physical activity, and lengthening breastfeeding duration could lower population breast cancer incidence substantially.

Socio-economic distribution of environmental risk factors for childhood injury.

OBJECTIVE: Childhood injury remains the single most important cause of mortality in children aged between 1-14 years in many countries. It has been proposed that lower socio-economic status (SES) and poorer housing contribute to potential hazards in the home environment. This study sought to establish whether the prevalence of observed hazards in and around the home was differentially distributed by SES, in order to identify opportunities for injury prevention. METHODS: This study was a cross-sectional, random sample survey of primary school children from 32 schools in Brisbane. Interviews and house audits were conducted between July 2000 and April 2003 to collect information on SES (income, employment and education) and previously identified household hazards. RESULTS: There was evidence of a relationship between prevalence of household environmental hazards and household SES; however, the magnitude and direction of this relationship appeared to be hazard-specific. Household income was related to play equipment characteristics, with higher SES groups being more likely to be exposed to risk. All three SES indicators were associated with differences in the home safety characteristics, with the lower SES groups more likely to be exposed to risk. CONCLUSION: The differential distribution of environmental risk factors by SES of household may help explain the SES differential in the burden of injury and provides opportunities for focusing efforts to address the problem.

Mental health: a cause or consequence of injury? A population-based matched cohort study.

BACKGROUND: While a number of studies report high prevalence of mental health problems among injured people, the temporal relationship between injury and mental health service use has not been established. This study aimed to quantify this relationship using 10 years of follow-up on a population-based cohort of hospitalised injured adults. METHODS: The Manitoba Injury Outcome Study is a retrospective population-based matched cohort study that utilised linked administrative data from Manitoba, Canada, to identify an inception cohort (1988-1991) of hospitalised injured cases (ICD-9-CM 800-995) aged 18-64 years (n = 21,032), which was matched to a non-injured population-based comparison group (n = 21,032). Pre-injury comorbidity and post-injury mental health data were obtained from hospital and physician claims records. Negative Binomial regression was used to estimate adjusted rate ratios (RRs) to measure associations between injury and mental health service use. RESULTS: Statistically significant differences in the rates of mental health service use were observed between the injured and non-injured, for the pre-injury year and every year of the follow-up period. The injured cohort had 6.56 times the rate of post-injury mental health hospitalisations (95% CI 5.87, 7.34) and 2.65 times the rate of post-injury mental health physician claims (95% CI 2.53, 2.77). Adjusting for comorbidities and pre-existing mental health service use reduced the hospitalisations RR to 3.24 (95% CI 2.92, 3.60) and the physician claims RR to 1.53 (95% CI 1.47, 1.59). CONCLUSION: These findings indicate the presence of pre-existing mental health conditions is a potential confounder when investigating injury as a risk factor for subsequent mental health problems. Collaboration with mental health professionals is important for injury prevention and care, with ongoing mental health support being a clearly indicated service need by injured people and their families. Public health policy relating to injury prevention and control needs to consider mental health strategies at the primary, secondary and tertiary level.

Acute alcohol consumption and mechanism of injury.

OBJECTIVE: The purpose of this study was to determine whether injury mechanism among injured patients is differentially distributed as a function of acute alcohol consumption (quantity, type, and drinking setting). METHOD: A cross-sectional study was conducted between October 2000 and October 2001 in the Gold Coast Hospital Emergency Department, Queensland, Australia. Data were collected quarterly over a 12-month period. Every injured patient who presented to the emergency department during the study period for treatment of an injury sustained less than 24 hours prior to presentation was approached for interview. The final sample comprised 593 injured patients (males=377). Three measures of alcohol consumption in the 6 hours prior to injury were obtained from self-report: quantity, beverage type, and drinking setting. The main outcome measure was mechanism of injury, which was categorized into six groups: road traffic crash (RTC), being hit by or against something, fall, cut/piercing, overdose/poisoning, and miscellaneous. Injury intent was also measured (intentional vs. unintentional). RESULTS: After controlling for relevant confounding variables, neither quantity nor type of alcohol was significantly associated with injury mechanism. However, drinking setting (i.e., licensed premise) was significantly associated with increased odds of sustaining an intentional versus unintentional injury (odds ratio [OR] = 2.79, 95% confidence interval [CI] = 1.4-5.6); injury through being hit by/against something versus other injury types (OR = 2.59, 95% CI = 1.4-4.9); and reduced odds of sustaining an injury through RTC versus non-RTC (OR = 0.02, 95% CI = 0.004-0.9), compared with not drinking alcohol prior to injury. CONCLUSIONS: No previous analytical studies have examined the relationship between injury mechanism and acute alcohol consumption (quantity, type, and setting) across all types of injury and all injury severities while controlling for potentially important confounders (demographic and situational confounders, risk-taking behavior, substance use, and usual drinking patterns). These data suggest that among injured patients, mechanism of injury is not differentially distributed as a function of quantity or type of acute alcohol consumption but may be differentially distributed as a function of drinking setting (i.e., RTC, intentional injury, being hit). Therefore, prevention strategies that focus primarily on the quantity and type of alcohol consumed should be directed generically across injury mechanisms and not limited to particular cause of injury campaigns.

Repeatability of self-reported information for population-based studies of cancer.

PURPOSE: To measure the repeatability of a cancer risk factor questionnaire in a population-based case-control study. METHODS: Questionnaires were completed on two occasions by patients with cancer of the ovary (n=25) or esophagus (n=23) and by 37 controls without cancer. We assessed general cancer risk factors including height and weight (for calculating body mass index (BMI)), smoking and anti-inflammatory (NSAID) use. Risk factors specific for ovarian and esophageal cancers were also assessed. Agreement was measured by the correlation coefficient and weighted kappa statistic (kw) for continuous and categorical variables respectively. RESULTS: We observed very high levels of agreement for BMI (kw=0.84) and smoking history, including ages at initiation and quitting (Pearson correlation = 0.87 and 0.86 respectively). There was moderate to substantial agreement for use of anti-inflammatory drugs (aspirin kw =0.52, other NSAIDS kw =0.72). Agreement for lifetime prevalence of medical conditions varied from almost perfect (e.g. history of benign breast disease (k =0.86)) to moderate (e.g. heartburn (k =0.57)). Item repeatability was not materially altered by case-control status, age or sex of respondents or interval between completions. CONCLUSIONS: Self-reported cancer risk factor information demonstrates moderate to almost perfect levels of agreement, suggesting these items are suitable for risk estimation and epidemiologic inference.

Searching for cancer deaths in Australia: National Death Index vs. cancer registries.

OBJECTIVE: To compare the accuracy, costs and utility of using the National Death Index (NDI) and state-based cancer registries in determining the mortality status of a cohort of women diagnosed with ovarian cancer in the early 1990s. METHODS: As part of a large prognostic study, identifying information on 822 women diagnosed with ovarian cancer between 1990 and 1993, was simultaneously submitted to the NDI and three state-based cancer registries to identify deceased women as of June 30, 1999. This was compared to the gold standard of "definite deaths". A comparative evaluation was also made of the time and costs associated with the two methods. RESULTS: Of the 450 definite deaths in our cohort the NDI correctly identified 417 and all of the 372 women known to be alive (sensitivity 93%, specificity 100%). Inconsistencies in identifiers recorded in our cohort files, particularly names, were responsible for the majority of known deaths not matching with the NDI, and if eliminated would increase the sensitivity to 98%. The cancer registries correctly identified 431 of the 450 definite deaths (sensitivity 96%). The costs associated with the NDI search were the same as the cancer registry searches, but the cancer registries took two months longer to conduct the searches. CONCLUSIONS AND IMPLICATIONS: This study indicates that the cancer registries are valuable, cost effective agencies for follow-up of mortality outcome in cancer cohorts, particularly where cohort members were residents of those states. For following large national cohorts the NDI provides additional information and flexibility when searching for deaths in Australia. This study also shows that women can be followed up for mortality with a high degree of accuracy using either service. Because each service makes a valuable contribution to the identification of deceased cancer subjects, both should be considered for optimal mortality follow-up in studies of cancer patients.

Injury severity: role of alcohol, substance use and risk-taking.

OBJECTIVE: The objective of the present study was to quantify the relationship between acute alcohol consumption and injury severity. METHODS: A cross-sectional study was conducted at the Gold Coast Hospital, Gold Coast, Queensland, Australia between October 2000 and October 2001. Data were collected from a systematic sample of patients greater than 15 years of age who presented to the ED for treatment of an injury sustained less than 24 h prior to presentation. Study participants were interviewed face to face on-site. Information obtained included: demographics details; situational variables relative to time of injury (i.e. location, activity and companions at time of injury); self-reported alcohol consumption in the 6 and 24 h prior to time of injury; usual alcohol consumption patterns; self-reported substance use in the 6 and 24 h prior to time of injury; and risk-taking behaviour. Injury severity was coded from patient medical records using the New Injury Severity Score. RESULTS: Of 789 eligible patients presenting during the study periods, 593 were interviewed (75.2%). Patients who reported drinking above low-risk levels (odds ratio [OR] = 3.35; 95% confidence interval [CI] 1.2-9.6) or who drank beer (OR = 3.54; 95% CI 1.1-11.1) in 6 h prior to injury were significantly more likely to sustain serious than minor injury. Drinking setting and usual drinking patterns were not significantly associated with injury severity, either in crude analyses, or after adjusting for relevant variables. CONCLUSION: The results of the present study support the conclusion that among injured patients who presented for treatment at a large metropolitan ED, although acute alcohol consumption does not appear to be associated with minor or moderate injury, there is some evidence to suggest that acute alcohol consumption is associated with serious injury.

The androgen receptor CAG repeat polymorphism and modification of breast cancer risk in BRCA1 and BRCA2 mutation carriers.

INTRODUCTION: The androgen receptor (AR) gene exon 1 CAG repeat polymorphism encodes a string of 9-32 glutamines. Women with germline BRCA1 mutations who carry at least one AR allele with 28 or more repeats have been reported to have an earlier age at onset of breast cancer. METHODS: A total of 604 living female Australian and British BRCA1 and/or BRCA2 mutation carriers from 376 families were genotyped for the AR CAG repeat polymorphism. The association between AR genotype and disease risk was assessed using Cox regression. AR genotype was analyzed as a dichotomous covariate using cut-points previously reported to be associated with increased risk among BRCA1 mutation carriers, and as a continuous variable considering smaller allele, larger allele and average allele size. RESULTS: There was no evidence that the AR CAG repeat polymorphism modified disease risk in the 376 BRCA1 or 219 BRCA2 mutation carriers screened successfully. The rate ratio associated with possession of at least one allele with 28 or more CAG repeats was 0.74 (95% confidence interval 0.42-1.29; P = 0.3) for BRCA1 carriers, and 1.12 (95% confidence interval 0.55-2.25; P = 0.8) for BRCA2 carriers. CONCLUSION: The AR exon 1 CAG repeat polymorphism does not appear to have an effect on breast cancer risk in BRCA1 or BRCA2 mutation carriers.

Melanocytic nevi in very young children: the role of phenotype, sun exposure, and sun protection.

BACKGROUND: Melanocytic nevi are strongly associated with cutaneous melanoma, yet little is known about factors influencing nevus development in the first years of life. OBJECTIVE: We sought to identify phenotypic and environmental factors associated with nevus counts in very young children. METHODS: In a cluster prevalence survey, full body nevus counts and phenotypic assessments were conducted on 193 children aged 1 to 3 years. Information on each child's sun exposure and sun protection practices was obtained through parental questionnaire. RESULTS: High total nevus counts were associated with heavy facial freckling, time spent outdoors on weekends in summer, and Caucasian ethnicity. Low nevus counts were associated with dark skin color, ability to tan, and frequent application of sunscreen. Frequent wearing of hats was specifically associated with low nevus counts on the face, but not at other sites. CONCLUSIONS: Nevi are common at a very young age among children in Queensland, Australia, and are associated with sun exposure and freckling. Diligent sun protection practices appear to reduce nevus burden, even after accounting for the effects of phenotype and sun exposure factors. Primary prevention strategies aimed at reducing sun exposure in very early life may be effective in reducing nevus prevalence and melanoma risk.

The effects of twins, parity and age at first birth on cancer risk in Swedish women.

The effect of reproductive history on the risk of cervical, colorectal and thyroid cancers and melanoma has been explored but the results to date are inconsistent. We aimed to examine in a record-linkage cohort study the risk of developing these cancers, as well as breast, ovarian and endometrial cancers, among mothers who had given birth to twins compared with those who had only singleton pregnancies. Women who delivered a baby in Sweden between 1961 and 1996 and who were 15 years or younger in 1961 were selected from the Swedish civil birth register and linked with the Swedish cancer registry. We used Poisson regression to assess associations between reproductive factors and cancer. Twinning was associated with reduced risks of breast, colorectal, ovarian and uterine cancers, although no relative risks were statistically significant. The delivery of twins did not increase the risk of any cancers studied. Increasing numbers of maternities were associated with significantly reduced risks of all tumors except thyroid cancer. We found positive associations between a later age at first birth and breast cancer and melanoma, while there were inverse associations with cervix, ovarian, uterine and colorectal cancers. These findings lend weight to the hypothesis that hormonal factors influence the etiology of colorectal cancer in women, but argue against any strong effect of hormones on the development of melanoma or tumors of the thyroid.

The CYP3A4*1B polymorphism has no functional significance and is not associated with risk of breast or ovarian cancer.

CYP3A4 is involved in the metabolism of endogenous steroids, and an allelic variant, CYP3A4*1B, consisting of an A to G polymorphism within the 5'-flanking region termed the nifedipine-specific response element (NFSE) has been associated with high grade and advanced stage of prostate cancers. Because steroid hormone exposure is known to influence breast and ovarian cancer risk, we conducted case-control studies to assess the relationship between CYP3A4*1B and risk of breast or ovarian cancer. CYP3A4 NFSE genotype was determined in 951 breast cancer cases and 500 controls frequency matched for age and 488 ovarian cancer cases and 276 controls of similar age distribution. Case-control analyses and comparisons of genotype distributions were conducted by unconditional logistic regression. In addition, the functional significance of the CYP3A4*1B polymorphism was assessed by analysis of CYP3A4-reporter gene constructs transiently transfected into liver-derived cell lines and primary cultures of well-differentiated rat hepatocytes. The GG genotype was rare in all groups (0-0.4%). There was no risk of cancer associated with the AG/GG genotypes combined, with an OR (95% CI) of 0.86 (0.54-1.33) for breast cancer (P = 0.5), and 1.51 (0.80-2.89) for ovarian cancer (P = 0.2). Analysis of CYP3A4-luciferase constructs showed that CYP3A4*1B did not consistently affect reporter gene activity. Our data suggest that the CYP3A4*1B polymorphism is not associated with risk of breast or ovarian cancer. In support of this negative finding, in-vitro functional studies indicate that NFSE genotype is not a critical factor in the transcriptional activity of the CYP3A4 5'-flanking region, and is thus unlikely to modulate CYP3A4-mediated metabolism of steroids.

Timing of pregnancy and the risk of epithelial ovarian cancer.

Recent animal studies suggest that progestagen-induced apoptosis of transformed ovarian surface epithelial cells may underlie the observed protective effect of pregnancy on the risk of ovarian cancer. Assuming that increasing numbers of cells are transformed with advancing age, we postulated that the benefits of pregnancy would be greater for older than younger women and tested this hypothesis in a population-based case-control study. We conducted interviews with 620 parous women, ages 18-79 years, with histologically confirmed incident ovarian cancer and 723 parous controls of the same age. Detailed information was collected on reproductive history, as well as hormonal exposures, smoking, medical history, and other factors. We estimated the relative risk of ovarian cancer associated with births at different ages through multiple logistic regression models. After adjusting for parity, older age at first and last births, and shorter time since last birth were all associated with significantly reduced risks of ovarian cancer. Age at first birth and time since last birth were not associated with ovarian cancer when adjusted for each other, whereas age at last birth remained strongly protective [odds ratio (OR), 0.57; 95% confidence interval (CI), 0.36-0.90] among women >35 years versus women less than 25 years. The effect was independent of total parity (per year of age among women with one birth: OR, 0.93; 95%CI, 0.87-1.01; among women with four or more births: OR, 0.96; 95%CI, 0.90-1.02). Our finding that ovarian cancer risk is reduced by pregnancy at older ages is further evidence that pregnancy confers a benefit beyond anovulation and is consistent with the theory that ovarian surface epithelial cell apoptosis induced by pregnancy hormones may be the underlying protective mechanism.