ESTIMATING THE PROBABILITY OF LYMPHEDEMA FOLLOWING BREAST CANCER SURGERY

Breast cancer-related lymphedema is a chronic complication of breast cancer treatment. It can result not only in physical discomfort and disfigurement but also in substantial impairment of daily activities. The public health importance of this study is to determine what, if any, factors contribute to an increased risk of lymphedema as well as to establish which subgroups of patients are at increased risk. Once the factors that influence the development of lymphedema are clarified, such findings can be used to develop preventive measures. In 2006, a 1:2 matched case-control study was carried out to determine significant predictors associated with breast cancer-related lymphedema. The results of the study showed that infection of the dominant arm, level of hand use and BMI would be significant predictors to cause lymphedema. Although the development of lymphedema still needs to be taken into account in clinical practice, this case-control study confirmed that some of risk factors can be used in prediction of lymphedema for breast cancer survivors.Because there is no precise incidence of lymphedema at present, the present study used the incidence rate from an independent study to predict probabilities of lymphedema for a group of breast cancer survivors by utilizing some confirmed risk factors. This study used Bayes' Theorem to develop an estimator for the probability of lymphedema given various combinations of BMI, infection, and level of hand use. The delta method was used to estimate the variance of predicted lymphedema probabilities. The results consist of a list of lymphedema probabilities for different combinations of risk factors, as well as 95% confidence limits for these probabilities. Patients who have BMI 25kg/m2, infection, and medium/high of occupational/hobby hand use would have the highest risk of lymphedema (76.71%) after breast cancer surgery. The goal of this analysis is to address issues in lymphedema formation, to determine whether a set of confirmed risk factors can predict lymphedema, and to estimate the probability of lymphedema in the final model. A well-established lymphedema predicting system for the general breast cancer survivors should be seriously taken consideration in the future

Obesity and Heart Diseases, a Worsened Epidemic in Recent Decades

Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and metabolic diseases. Obesity induces serious heart diseases such as hypertension, heart failure, and coronary disease by multiple mechanisms. The endothelial dysfunction and artherosclerosis induced by obesity lead to the result of coronary artery disease. In addition, obesity is a substantial public health crisis worldwide, and internationally, with the prevalence increasing rapidly in numerous industrialized nations. Worldwide, 39% of adults aged 18 years and over were overweight in 2014, and 13% were obese. The first choice of treatment is weight loss by life-style modification, such as diet and exercise. Medication and surgery are for moderate obese patients with comorbidity. How to find the appropriate method of weight losing is the most important issue

Inference on conditional quantile residual life for censored survival data

For randomly censored data, the residual life function at a given time determines a life distribution of a subject survived up to that time point. In the situation where the data are censored, or where the underlying distribution is skewed, the quantile residual life function is preferred. A number of studies regarding the quantile residual lifetime have been conducted in the univariate settings by many professionals. However, when a pair of units are observed, i.e. a study of twins, or when patients experience two types of events, i.e. time to morbidity and time to mortality, a bivariate modelling of quantile residual lifetime subject to right censoring might be of utmost interest. In this dissertation, we develop the estimation of conditional quantile residual lifetime on semi-competing risks data. The proposed estimator is conditioning on the occurrence of the nonterminal event beyond time t. The covariate effects on specifc pairs of failure times are evaluated based on a log-linear regression on conditional quantile residual lifetime for semi-competing risks data. Numerical studies demonstrate a reasonable performance of the estimator for moderate sample sizes. The proposed method is applied to a study of breast cancer data from a phase III clinical trial. Public Health Significance: In many survival studies, bivariate correlated failure times can be observed in a pair or in the same individual experiencing multiple failure times. It is of interest to know the additional time to failure of a surviving unit, when another unit is known to have failed at an earlier time. In this dissertation, the proposed estimator of the residual lifetime given the occurrence of a failure demonstrates the importance of lifetime expectancy that patients and their family seek to know before an onset of a new treatment

Shape restricted regression with random Bernstein polynomials

Shape restricted regressions, including isotonic regression and concave regression as special cases, are studied using priors on Bernstein polynomials and Markov chain Monte Carlo methods. These priors have large supports, select only smooth functions, can easily incorporate geometric information into the prior, and can be generated without computational difficulty. Algorithms generating priors and posteriors are proposed, and simulation studies are conducted to illustrate the performance of this approach. Comparisons with the density-regression method of Dette et al. (2006) are included.Comment: Published at http://dx.doi.org/10.1214/074921707000000157 in the IMS Lecture Notes Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

Design of automotive structural components using high strength sheet steels mechanical properties of materials (aging effect)

INTRODUCTION It has been known for years that mechanical properties of thin sheet steels, such as yield strength, tensile strength, and ductility, are affected by aging (Chajes et al. 1963, Hertzberg 1989, Yu 1991). The aging effect on mechanical properties can be described as follows. For a virgin steel that is initially loaded in tension beyond its yield strength and into strain hardening state and then unloaded to zero stress, the yield and tensile strengths of the steel increase while the ductility of the steel decreases if the steel is reloaded in tension again after a period of time from the first unloading. Due to diffusion of the carbon and nitrogen in steels and the fact that steel sheets are usually produced in a cold rolling process, in which the sheet steels undergo large plastic deformation, their mechanical properties can be affected by aging. Therefore, the mechanical properties of the thin sheet steels at the time when they are used can be different from the properties at the time when they are produced. The yield and tensile strengths of the sheet steels will increase over time while the ductility of the steels will decrease. In 1992, a research project, sponsored by the American Iron and Steel Institute (AISI), was carried out at the University of Missouri-Rolla to study the effect of strain rate on the mechanical properties of sheet steels (Pan and Yu 1992). In this research, coupons cut from two selected sheet steels (25AK and 50SK) were tested in longitudinal and transverse tension and compression at four different strain rates, namely 0.0001,0.01,0.1, and 1.0 in./in./sec.. The results of the study were reported by Pan and Yu (1992). Later on for another study on the strength of hybrid structural components made of these two steels (Pan and Yu 1995), the mechanical properties of the steels that were obtained in 1992 were used to evaluate the strength of the hybrid members without consideration of the aging effect. In this later study, the hybrid members were tested in bending at the strain rates of 0.0001 and 0.01 in./in./sec.. In order to estimate the aging effect on the mechanical properties of two types of sheet steels used by Pan and Yu (1992), additional coupon tests of the sheet steels (25AK and 50SK) were conducted at the University of Missouri-Rolla in August 1995 and in January 1997. A total of twenty coupons, ten for each steel, were tested at two different strain rates, namely 0.0001 and 0.01 in./in./sec.. Four coupons for each steel were tested at the strain rate of 0.0001 in./in./sec. in August 1995, while three coupons for each steel were tested at the strain rate of 0.0001 in./in./sec. in January 1997 and another three coupons for each steel were tested at the strain rate of 0.01 in./in./sec. at the same time. This report summarizes the results of the twenty coupon tests. In the following discussions, Section 2 presents the test results on the mechanical properties of25AK and 50SK sheet steels. Section 3 compares the mechanical properties of the steels reported by Pan and Yu (1992) with those presented in Section 2 to estimate the aging effect on steels and the computed yield moments. Finally, Section 4 summarizes the findings