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PubMed2002

The prognostic significance of Gail model risk factors for women with breast cancer.

BACKGROUND: Because many risk factors for breast cancer are related to hormonal factors and hormonal factors influence breast cancer prognosis, risk factors may have prognostic value. In order to assess the prognostic value of risk factors for breast cancer we divided patients with breast cancer into those at high risk and low risk using the Gail model. METHODS: Patients with available follow-up and information concerning age, age at menarche, number of children, age at first birth, number of first degree relatives with breast cancer, and number of previous breast biopsies were divided into low and high-risk groups by the average relative risk calculated using the Gail model. Risk factors, clinical presentations, pathologic findings, tumor characteristics, extent of disease, treatment and outcomes for the 106 high-risk women were compared with the 206 low-risk women. Stage IV patients were excluded. RESULTS: The average relative risk of breast cancer was 2.09. The 106 high-risk women were significantly older (58 years versus 53 years; P = 0.001), older at first live birth (30 years versus 23 years; P <0.001), more likely to have a first degree relative with breast cancer (57% versus 0%; P <0.001), and more likely to have previously had a breast biopsy (19% versus 1%; P <0.001). There was no difference in the average age at menarche. Low-risk patients were significantly more frequently nulliparous (40% versus 22%; P = 0.002). Clinical presentation, pathologic findings, extent of disease, and treatment were comparable in high and low-risk patients. Cancers of low-risk patients were more frequently poorly differentiated (39% versus 25%, P = 0.044). Tamoxifen was used more frequently in high-risk patients (56% versus 41%; P = 0.012). High-risk patients exhibited significantly better 5-year (95% versus 88%; P = 0.047) and 10-year distant disease-free survival than low-risk patients (88% versus 79%; P = 0.050). In multivariate analysis only the number of involved lymph nodes was related to local (P = 0.001) and distant (P <0.001) disease-free survival. CONCLUSIONS: Breast cancer patients considered high risk by the Gail model have significantly better disease-free survival than low-risk patients. This study does not support the notion that risk factors for breast cancer are prognostic factors.

Adult↗
PubMed2000

Risk models for familial ovarian and breast cancer.

We investigated risk models for the inherited susceptibility of breast and ovarian cancer, using data from both high-risk families and a population based series of ovarian cancer. The first data set consisted of 112 families containing two or more relatives with epithelial ovarian cancer. BRCA1 and BRCA2 germline mutations were detected in 50% of these families. The second study involved 374 ovarian cancer cases, unselected for family history, who had DNA samples analyzed for BRCA1 mutations. Twelve women were found to be carriers. We constructed genetic models for ovarian and breast cancer using the computer program MENDEL. In the first study, we modeled the effects of BRCA1 and BRCA2 simultaneously and allowed for a third gene predisposing to ovarian cancer. None of the models fitted gave significant evidence for a third gene. Population frequencies of BRCA1 and BRCA2 mutations were estimated to be 0. 00128 and 0.00172, respectively. Our results suggest that BRCA1 and BRCA2 may be sufficient to explain the majority of familial ovarian cancer and that families without mutations can be explained by sensitivity of mutation testing and chance clusters of sporadic cases. Using data on the families of the 12 mutation carriers in the second study, we estimated age-specific ovarian and breast cancer risks for BRCA1 mutation carriers. Under the best-fitting model, the cumulative ovarian cancer risk was 66% by age 70, and the corresponding breast cancer risk was 45%. The high penetrance estimate for ovarian cancer, compared with other studies, suggests that modifying genetic or environmental factors may be important determinants of risk.

Breast Neoplasms↗
PubMed1998

Cost-effectiveness of pravastatin in secondary prevention of coronary heart disease: comparison between Belgium and the United States of a projected risk model.

Methodological differences and variations in health care regulations among countries often preclude direct comparisons of cost-effectiveness studies. A projected risk model was applied, designed to determine the economic value in the United States of pravastatin in the secondary prevention of coronary heart disease (CHD), to Belgium using local health care costs. A Markov process was used to model the effectiveness of treatment for 3 years with pravastatin versus placebo in 1000 male CHD patients aged 60 years and clinically similar to those in the pravastatin limitation of atherosclerosis in the coronary arteries (PLAC I) and pravastatin, lipids and atherosclerosis in the carotid arteries (PLAC II) studies. The PLAC I and II trials have shown that pravastatin treatment for 3 years at a weighted mean dose of 36.64 mg daily significantly reduced the incidence of non-fatal myocardial infarction in patients with CHD. Framingham data were used to project the risk of mortality 10 years post-myocardial infarction. The incremental cost per life year gained (LYG), after discounting costs and benefits by 5% annually, in the setting of Belgian health care regulations, was Belgian francs (BEF) 720794 (US$ 24359) for CHD patients with one additional risk factor; BEF 526464 (US$ 17792) for those with two additional risk factors; and BEF 392765 (US$ 13274) for those with three or more additional risk factors. The cost per LYG in Belgium appeared to be more sensitive to drug acquisition cost than to costs of medical interventions. The cost-effectiveness ratios of pravastatin monotherapy for 3 years in secondary prevention of CHD, obtained with the same projected risk model, are from 86 to 92% higher in Belgium than in the United States, due to differences in medical patterns of practice and in intervention costs.

Anticholesteremic Agents↗
PubMed2001

Receiver operating characteristic curve analysis of clinical risk models.

Receiver operating characteristic (ROC) curve analysis is a useful method to measure the ability of a clinical risk model to discriminate between hospital deaths and survivors. Its use in medicine originated as a method for synthesizing the specificity and sensitivity of diagnostic tests across a spectrum of possible cut points. The area under the ROC curve can be interpreted as a probability of correct classification or prediction. We illustrate its use in three steps: first, with a dichotomous variable to introduce specificity and sensitivity; next, with a categorical risk factor (surgical urgency) to produce a primitive ROC curve; and finally, with a continuous risk factor (age) to approximate the usual ROC curve used for clinical risk models.

Adult↗
PubMed2001

A triple-risk model for the sudden infant death syndrome (SIDS) and the apparent life-threatening episode (ALTE): the stressed magnesium deficient weanling rat.

A triple risk model for the sudden infant death syndrome (SIDS) as described by Filiano and Kinney involves the intersection of three risks: (1) a vulnerable infant, (2) a critical developmental period in homeostatic control, and (3) an exogenous stressor(s). The triple risk model aptly describes the dynamics of an animal model for SIDS: (1) a vulnerable animal that is young and magnesium deficient: (2) a critical developmental period revealed by hyperirritability, labile cardiovascular and respiratory control; and (3) an exogenous stressor such as soft, high-pitched noise; motion or handling; or a chill. Together these three risks may trigger a shock-like episode of apnea, unconsciousness and bradycardia. The lung is the shock organ. An animal that dies quietly or after physical activity following the episode, models SIDS. However, if the shock-like episode resolves spontaneously or after resuscitation, the survivor is a model for an apparent life-threatening episode (ALTE). If, while still in the critical developmental period the ALTE survivor is stressed again, there is a risk for a recurrent episode, with the final outcome still unpredictable but with increasing risk for SIDS with multiple recurrences. The purpose of this communication is to present an illustrated review of the magnesium deficient weanling rat as an animal model for SIDS/ALTE, showing pertinent physical, electrocardiographic and pathological features. In the weanling rat, magnesium deficiency appears to be the single common pathway upon which multiple stressors may impinge to produce sudden death during the relatively brief critical developmental period, while magnesium supplements may protect the animal. If significant magnesium deficiency is subsequently diagnosed in a properly controlled study of human SIDS tissue, it is likely that a high proportion of SIDS deaths could be prevented by simple oral magnesium supplementation to infants during the first critical weeks and months of life.

Animals↗
PubMed1998

Preoperative risk models for minimally invasive coronary bypass: a preliminary study.

OBJECTIVE: Available risk assessment models are designed for standard coronary artery bypass grafting. We hypothesized that minimally invasive coronary bypass could improve on predicted outcome in extremely high-risk patients (Parsonnet score > 20%) by the current risk models. METHODS: From September 1996 to September 1997, 27 consecutive extremely high-risk patients underwent minimally invasive coronary bypass. Seventeen patients were male; age was 73 +/- 12 years, and 63% of patients were older than 75 years. Left ventricular ejection fraction was 33.7% +/- 15% and 63% had an ejection fraction of less than 35%. The predicted 30-day mortality according to the System 97 model was 25.6% +/- 11.3%. The Parsonnet risk score was 36.2% +/- 11%; the predicted length of stay in the hospital was 15.3 +/- 3 days. The predicted risk of stroke according to the Multicenter Perioperative Stroke Risk Index was 22.3% +/- 11.7%. RESULTS: Minimally invasive coronary bypass was isolated in 20 patients and integrated with angioplasty and stenting in 7 patients. The observed 30-day mortality was 0% (P < .01 vs predicted): at an average follow-up of 10.8 +/- 4.1 months, 26 patients (96.3%) are alive without angina; one patient with acquired immunodeficiency syndrome died on postoperative day 40 of acute pancreatitis. No patient had a stroke or neurologic deficit (P < .01 vs predicted). Patency of internal thoracic artery anastomosis was confirmed by angiography in all 27 patients. No patient required reoperation. Eighteen patients (67%) were extubated in the operating room. The observed length of hospital stay after minimally invasive coronary bypass was 3.8 +/- 2.6 days (P < .01 vs predicted). CONCLUSION: On the basis of our results on a relatively small series of patients, we suggest that risk models geared for standard coronary bypass grafting may not be appropriate for minimally invasive coronary bypass.

Aged↗
PubMed1995

Somatization. Concepts, data, and predictions from the high risk model of threat perception.

Eighty-three consecutive patients with chronic somatic complaints seen prior to therapy were tested on the eight factors of the High Risk Model of Threat Perception. Thirty-two percent were high and 28% were low on hypnotic ability, which is more highs and lows than would be expected in a normal population. In the high and low hypnotic ability somatizers, the distribution of somatic and psychological symptoms is significantly different from the moderate group. Counterintuitively, hypnotic ability and major life change were orthogonal to all of the other risk factors. These findings are consistent with eight of nine predictions from the High Risk Model of Threat Perception.

Adaptation, Psychological↗
PubMed1998

Uncertainty and variability analysis in multiplicative risk models.

Currently, there is a trend away from the use of single (often conservative) estimates of risk to summarize the results of risk analyses in favor of stochastic methods which provide a more complete characterization of risk. The use of such stochastic methods leads to a distribution of possible values of risk, taking into account both uncertainty and variability in all of the factors affecting risk. In this article, we propose a general framework for the analysis of uncertainty and variability for use in the commonly encountered case of multireplicative risk models, in which risk may be expressed as a product of two or more risk factors. Our analytical methods facilitate the evaluation of overall uncertainty and variability in risk assessment, as well as the contributions of individual risk factors to both uncertainty and variability which is cumbersome using Monte Carlo methods. The use of these methods is illustrated in the analysis of potential cancer risks due to the ingestion of radon in drinking water.

Analysis of Variance↗
PubMed1998

Analysis of the treatment effect on recurrent bleeding and death in patients with cirrhosis and esophageal varices: multistage competing-risks model compared to conventional methods. The Copenhagen Esophageal Varices Sclerotherapy Project.

BACKGROUND/AIMS: Multiple recurrences of bleeding with high mortality in cirrhosis with esophageal varices have been inadequately analyzed in previous trials. We propose analysis by the multistage competing-risks model, specifying the effect on overall mortality as an effect on mortality during bleeding, rate of cessation of bleeding, mortality rate without bleeding, and rate of rebleeding. METHODS: The Copenhagen Esophageal Varices Project enrolled patients after first bleeding and randomized 94 to usual treatment and 93 to sclerotherapy as supplement. During 9-52 months of follow-up, rebleeding occurred in 49 and 42, and death in 68 and 60 patients, respectively. The proportional hazards regression model (Cox model) was used for reanalysis both by the multistage competing-risks model and by conventional analysis for overall mortality and rate of first rebleeding. In the multistage model, time zero was at entry to any new disease stage, of which the first four were analyzed - two bleeding stages and two bleeding-free stages. RESULTS: The conventional analysis showed a reduction of overall mortality rate in the sclerotherapy group of borderline significance, but no effect on rate of rebleeding. The multistage model indicated that sclerotherapy reduced the rate of rebleeding late in the disease course, and particularly after the first rebleeding. Rate of cessation of bleeding and mortality rates during bleeding and without bleeding were not affected by sclerotherapy. CONCLUSIONS: Conventional analysis may give misleading conclusions, which might be avoided by applying the multistage model. The effect of sclerotherapy on overall mortality may be ascribed entirely to the reduced rate of rebleeding.

Denmark↗
PubMed2003

Validation of the Hendrich II Fall Risk Model: a large concurrent case/control study of hospitalized patients.

This large case/control study of fall and non-fall patients, in an acute care tertiary facility, was designed to concurrently test the Hendrich Fall Risk Model. Cases and controls (355/780) were randomly enrolled and assessed for more than 600 risk factors (intrinsic/extrinsic). Standardized instruments were used for key physical attributes as well as clinician assessments. A risk factor model was developed through stepwise logistic regression. Two-way interactions among the risk factors were tested for significance. The best fitting model included 2 Log L chi square statistic as well as sensitivity and specificity values retrospectively. The result of the study is an easy to use validated Hendrich Fall Risk Model with eight assessment parameters for high-risk fall identification tested in acute care environments.

Accidental Falls↗
PubMed2003

The use of biologically based cancer risk models in radiation epidemiology.

Biologically based risk projection models for radiation carcinogenesis seek to describe the fundamental biological processes involved in neoplastic transformation of somatic cells into malignant cancer cells. A validated biologically based model, whose parameters have a direct biological interpretation, can also be used to extrapolate cancer risks to different exposure conditions with some confidence. In this article biologically based models for radiation carcinogenesis, including the two-stage clonal expansion (TSCE) model and its extensions, are reviewed. The biological and mathematical bases for such models are described, and the implications of key model parameters for cancer risk assessment examined. Specific applications of versions of the TSCE model to important epidemiological datasets are discussed, including the Colorado uranium miners' cohort; a cohort of Chinese tin miners; the lifespan cohort of atomic bomb survivors in Hiroshima and Nagasaki; and a cohort of over 200,000 workers included in the National Dose Registry (NDR) of Canada.

Canada↗
PubMed2001

Functional and structural measurements in a multifactorial glaucoma risk model.

PURPOSE: To evaluate the relationship between a multifactorial probability risk model of developing glaucomatous visual field defects and the assessment of the retinal nerve fiber layer (RNFL) and short-wavelength automated perimetry (SWAP) in glaucoma suspects. METHODS: 157 eyes of 157 glaucoma suspects were included in the study. The risk of developing glaucomatous defects was assessed by applying a multifactorial model that included intraocular pressure, vertical cup-to-disk ratio, age and family history. Photographs of the RNFL and SWAP were performed. RESULTS: The SWAP was abnormal in 54 cases (34.3%); 21% of abnormal perimetries were obtained in the low-risk group, 37% in the moderate risk group and 56% in the high risk group. The nerve fiber layer evaluation in the different risk stages showed a pattern similar to the results obtained with SWAP. Multiple regression analyses, performed with the four variables included in the model with SWAP and RNFL evaluation, showed the relationship between the risk factors and the presence of glaucomatous damage--evaluated by RNFL and SWAP (p<0001). CONCLUSIONS: The probability model showed a good correlation between the risk scale and the RNFL and SWAP assessment.

Adult↗
PubMed1994

A perspective on neuropathologic findings in victims of the sudden infant death syndrome: the triple-risk model.

Neuropathologic studies in SIDS victims support the concept that they are not entirely 'normal' prior to death, but rather possess underlying vulnerabilities which put them at risk for sudden death. This concept forms a key link in a triple-risk model for the pathogenesis of SIDS proposed by us. According to this model, sudden death in SIDS results from the intersection of three overlapping factors: (1) a vulnerable infant; (2) a critical developmental period in homeostatic control, and (3) an exogenous stressor(s). An infant will die of SIDS only if he/she possesses all three factors; the infant's vulnerability lies latent until he/she enters the critical period and is subject to an exogenous stressor. According to this model, heterogeneous disorders may make the infant vulnerable to sudden death during the critical period, as potentially exemplified by two previously reported lesions in SIDS brains (arcuate nucleus hypoplasia and subtle hypomyelination). Nevertheless, the triple-risk model does not preclude the possibility that the majority of SIDS deaths will be explained by a single common pathway upon which multiple stressors impinge to produce sudden death during the critical period.

Brain↗
PubMed1999

Risk model for severe anemia requiring red blood cell transfusion after cytotoxic conventional chemotherapy regimens. The Elypse 1 Study Group.

PURPOSE: Cancer patients frequently experience anemia as a consequence of myelosuppressive therapy or bone marrow invasion. PATIENTS AND METHODS: A risk model for chemotherapy-induced severe anemia requiring RBC transfusions (SARRT) within 31 days after the administration of chemotherapy was delineated in the cohort of cancer patients treated with chemotherapy in the Department of Medicine of Centre Léon Bérard in 1996 (CLB-1996). The risk model was tested on a series of 797 patients treated in 1997 (CLB-1997) and on 295 patients included in a multicenter prospective series (ELYPSE 1). RESULTS: One hundred seven of the 1,051 patients of the CLB-1996 cohort (10%) experienced SARRT. In univariate analysis, only female sex, performance status greater than 1, hemoglobin level less than 12 g/dL before chemotherapy on day 1 (d1), and d1 lymphocyte count < or = 700/microL significantly correlated with the risk of SARRT. Using logistic regression, d1 hemoglobin level less than 12 g/dL (odds ratio [OR] = 14.0; 95% confidence interval [CI], 7 to 30), performance status greater than 1 (OR = 2.2; 95% CI, 1.4 to 3.5), and d1 lymphocyte count < or = 700/microL (OR = 1.7; 95% CI, 1. 1 to 2.6) were identified as independent risk factors for SARRT. These three factors were given arbitrary risk coefficients of 3, 1, and 1 respectively, and a risk score for each individual patient was obtained by adding the coefficients. The calculated probability of RBC transfusions was 30% for patients with a score > or = 4, and 11%, 4%, and 1% in patients with a score of 2 or 3, 1, and 0 respectively. This model was then tested and validated in the CLB-1997 and ELYPSE 1 series. CONCLUSION: This risk index could be useful to identify patients at high risk for chemotherapy-induced SARRT who might be appropriate candidates for prophylactic erythropoietin treatment.

Adolescent↗
PubMed2002

Survival and risk model for stage IB non-small cell lung cancer.

BACKGROUND: The aim of this work is to estimate the prognostic value of a set of clinical-pathological factors in patients resected for non-small cell lung cancer (NSCLC) and classified as stage IB, in order to create a prognostic model for establishing risk groups, and to validate that model. METHODS: Among 637 patients resected and classified as stage IB, we analyzed sex, age, symptoms, location, type of resection, cell type, histology, and tumor size. The Kaplan-Meier method was used to estimate the survival. The results were compared using the log-rank test. All the significant variables from this univariable method were then included in a multivariable method of estimation of the proportional risk for survival data developed by Cox, using the variables selected, a regression model was developed for accurately predicting survival. To validate the predictive capability of the regression model, we randomly divided our patients into training and test subsets, containing 322 and 315 cases, respectively. RESULTS: The overall 5-year survival rate of the series was 60%. The cell type, the squamous or non-squamous and the tumor size showed a significant influence on survival in the univariable analysis, while, according to the Cox model, only the tumor size and the squamous or non-squamous type entered into regression. Hazard rates were calculated for each patient. The mean risk was 0.87 +/- 0.25 (range 30-1.94). The series was divided into three risk groups (low, intermediate, and high risk) according to the fitted hazard rates, using cut-off points (one standard deviation from the mean). The 5-year survival rates were 85, 59, and 44%, respectively. To validate the model, we repeated the analysis for training and test subsets. Only the tumor size had a significant influence on survival in the univariable analysis. Using the Cox model, also the tumor size entered into regression. The mean risk was 0.79 +/- 0.29 (range 0.09-2.12). Cut-off points were 0.50 and 1.08 for the low, intermediate, and high-risk groups. The 5-year survival rates were 83, 58, and 40%, respectively. We validated the regression model obtained in the training subset by demonstrating its capacity in identifying risk groups in the test subset. The 5-year survival rates were 83, 61, and 49.5% for the low, intermediate, and high-risk groups, respectively (P = 0.0104). CONCLUSIONS: Stage IB does not succeed in configuring a group of patients with a homogeneous prognosis, as there is a wide variability in a 5-year survival. The estimation of prognosis derived from a multivariable analysis can obviate the limitations of the actual staging system for NSCLC.

Adenocarcinoma↗
PubMed2003

Correlations between parameters in risk models: estimation and propagation of uncertainty by Markov Chain Monte Carlo.

Monte Carlo simulation has become the accepted method for propagating parameter uncertainty through risk models. It is widely appreciated, however, that correlations between input variables must be taken into account if models are to deliver correct assessments of uncertainty in risk. Various two-stage methods have been proposed that first estimate a correlation structure and then generate Monte Carlo simulations, which incorporate this structure while leaving marginal distributions of parameters unchanged. Here we propose a one-stage alternative, in which the correlation structure is estimated from the data directly by Bayesian Markov Chain Monte Carlo methods. Samples from the posterior distribution of the outputs then correctly reflect the correlation between parameters, given the data and the model. Besides its computational simplicity, this approach utilizes the available evidence from a wide variety of structures, including incomplete data and correlated and uncorrelated repeat observations. The major advantage of a Bayesian approach is that, rather than assuming the correlation structure is fixed and known, it captures the joint uncertainty induced by the data in all parameters, including variances and covariances, and correctly propagates this through the decision or risk model. These features are illustrated with examples on emissions of dioxin congeners from solid waste incinerators.

Journal Article↗
PubMed1999

Application of the high risk model of threat perception to a primary care patient population.

This study was designed to test the hypothesis that patients with a tendency to somatize psychological distress into physical symptoms could be differentiated from patients who do not somatize on the basis of specific predisposing factors defined by the High Risk Model of Threat Perception. Patients in a family practice were assessed for the tendency to somatize by the Diagnostic Interview Schedule (DIS) and by physician rating. Twenty-seven percent of the patients were positive for tendency to somatize by physician rating. These patients had relatively high negative affect, absorption, catastrophizing, self-reported pain and stress, and greater utilization of services. None of the patients assessed by the DIS met criteria for somatization disorder, but 28% were positive for somatoform pain disorder. These patients also scored higher on the negative affect questionnaire, tended to have higher absorption scores, reported greater pain and stress, and utilized more services. Results of this study are partially supportive of the High Risk Model of Threat Perception, because two of the predisposer factors were associated both with tendency to somatize by physician rating and with somatoform pain disorder by interview. The higher utilization of services in the somatizing patients has cost and service ramifications. Treatment of patients with tendencies to somatize within a family practice setting are discussed.

Causality↗
PubMed2000

Factors influencing blood pressure: development of a risk model.

A review of the literature suggests that blood pressure (BP) is multifactorial and is affected by the interactions of genetics, physiology, responses to the environment, and lifestyle factors that have increasing influence as one ages. The effect of these factors on hypertension (HTN) risk as one ages is depicted in the author's Hypertension Risk Model. The model emphasizes HTN risk in the older adult--age 50 and older--and shows the interaction of the factors influencing HTN development and BP assessment methods. Implications of three methods of BP assessment--(1) static BP, (2) 24-hour ambulatory blood pressure monitoring, and (3) clinic blood pressure reactivity (BPR) protocol--are discussed. The model may be useful for understanding factors that contribute to HTN and for guiding BP assessment for clinical researchers. Addressing the factors associated with the sympathetic system activity from various environmental stressors requires assessing dynamic BP, particularly in the older hypertensive adult who has increased BPR. Further research should focus on ambulatory blood pressure studies in older adults that would provide the methods and instrumentation needed to assess HTN and therefore decrease mortality and morbidity in this population.

Blood Pressure Determination↗