Jacob Cohen

Bio: Jacob Cohen is an academic researcher from State University of New York System. The author has contributed to research in topics: Prostate cancer & Competence (human resources). The author has an hindex of 5, co-authored 6 publications receiving 104080 citations. Previous affiliations of Jacob Cohen include SUNY Downstate Medical Center & University of North Carolina at Chapel Hill.

Statistical Power Analysis for the Behavioral Sciences

Abstract: Contents: Prefaces. The Concepts of Power Analysis. The t-Test for Means. The Significance of a Product Moment rs (subscript s). Differences Between Correlation Coefficients. The Test That a Proportion is .50 and the Sign Test. Differences Between Proportions. Chi-Square Tests for Goodness of Fit and Contingency Tables. The Analysis of Variance and Covariance. Multiple Regression and Correlation Analysis. Set Correlation and Multivariate Methods. Some Issues in Power Analysis. Computational Procedures.

Ureteropyeloscopic treatment of large, complex intrarenal and proximal ureteral calculi

Abstract: UNLABELLED: Study Type - Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? Large upper tract urinary calculi, greater than 2 cm, have historically been treated with percutaneous nephrostolithotomy. In general, there has been a growing interest in employing retrograde, flexible ureteroscopy and laser lithotripsy in select patients who are either poor medical candidates for percutaneous lithotripsy or who may prefer a less invasive intervention. Properly selecting patients for this approach, designing specific treatments based on complex stone presentation and offering general information with regard to long-term outcomes and surgical risks have historically been based on results from small, multicentre series lacking uniformity of technique and long-term outcomes. Our initial multicentre experience employing ureteroscopic techniques to treat large upper urinary tract calculi was presented in 1998. This current work represented the largest single-centre experience, accrued prospectively over 10 years, where there was uniformity of technique and treatment algorithms. This study frames an argument for retrograde ureteroscopic lithotripsy not only in those who are at high risk for percutaneous nephrostolithotomy but in all who present with large, non-infected stone burdens. OBJECTIVE: To define the safety and efficacy of retrograde ureteroscopic lithotripsy in treating large, non-infectious intrarenal and proximal ureteral stone burdens. PATIENTS AND METHODS: Between 2000 and 2011, 145 patients with 164 large (2 cm or greater in diameter on standard imaging) non-infectious upper intrarenal and proximal ureteral calculi were chosen for retrograde ureteroscopic lithotripsy. Patients were treated with small diameter flexible fibre-optic ureteroscopes and holmium laser lithotripsy by a single surgeon. Second-look ureteroscopy was performed in patients with the largest calculi in whom there was a high index of suspicion of significant residual fragments. Stone clearance was defined as no fragments or a single fragment less than or equal to 4 mm in diameter on standard radiograph and sonography at 3-month follow-up. RESULTS: Our study included 103 male patients and 42 female patients with an average age of 55 years (range 16-86 years) and a mean stone diameter of 29 mm (range 20-70 mm) including 36 partial staghorn stone burdens (mean diameter 37 mm). Overall, 266 ureteroscopies were performed on 164 stone burdens (1.6 procedures per stone burden), clearing 143 stone burdens (87%). The highest clearance rates were observed for proximal ureteral (97%) and renal pelvic (94%) stones, while the lowest clearance rates were observed for lower pole (83%) and staghorn calculi (81%). Three patients required subsequent percutaneous therapy due to infectious material encountered at the time of ureteroscopy or inaccessible stone burdens secondary to infundibular stenosis. There were five minor postoperative complications, including four fevers and one patient with gross haematuria and clot retention, with no major intraoperative complications. CONCLUSIONS: In select patients, large, complex, metabolic upper urinary tract calculi can be treated safely and efficiently with retrograde ureteroscopic techniques. Staged, retrograde, flexible ureteroscopy is an alternative to percutaneous therapy with acceptable efficacy and low morbidity.

Racial differences in clinical progression among Medicare recipients after treatment for localized prostate cancer (United States).

Abstract: Prostate cancer recurrence impacts patient quality of life and risk of prostate-cancer specific death following definitive treatment. We investigate differences in disease-free survival among white, black, Hispanic, and Asian patients in a large, population-based database. Merged Surveillance, Epidemiology, and End Results Program (SEER) and Medicare files provided data on 23,353 white patients, 2,814 black patients, 480 Hispanic patients, and 566 Asian patients diagnosed at age 65–84 years with clinically localized prostate cancer between 1986 and 1996 in five SEER sites. Patients were followed through 1998. Racial differences in disease-free survival were assessed using Kaplan–Meier survival curves and Cox regression models. The 75th percentile disease-free survival time for black patients was 13 months less than that for white patients (95% confidence interval [CI]: 6.2–19.8 months), 29.7 months less than that for Hispanic patients (95% CI: 4.4–55.0 months), and 39.1 months less than that for Asian patients (95% CI: 12.1–66.1 months). In multivariate analysis, black race predicted shorter disease-free survival among surgery patients, but not among radiation patients. Black patients experienced shorter disease-free survival compared to white, Hispanic, and Asian patients, and the disease-free survival of white, Hispanic, and Asian patients were not statistically different. Earlier recurrence of prostate cancer may help explain black patients’ increased risk of mortality from prostate cancer.

Racial differences in clinical progression among Medicare recipients after treatment for localized prostate cancer3

Abstract: Objective Prostate cancer recurrence impacts patient quality of life and risk of prostate-cancer specific death following definitive treatment. We investigate differences in disease-free survival among white, black, Hispanic, and Asian patients in a large, population-based database. Methods Merged Surveillance, Epidemiology, and End Results Program (SEER) and Medicare files provided data on 23,353 white patients, 2,814 black patients, 480 His? panic patients, and 566 Asian patients diagnosed at age 65 84 years with clinically localized prostate cancer between 1986 and 1996 in five SEER sites. Patients were followed

Outcomes following negative prostate biopsy for patients with persistent disease after radiotherapy for prostate cancer.

Abstract: PURPOSE: When faced with biochemical recurrence after definitive radiotherapy for prostate cancer, clinicians must determine whether the recurrence is local or systemic. Post radiotherapy prostate biopsies to detect persistent local disease are difficult to interpret histopathologically and are subject to sampling error. Our study examines outcomes for patients with a negative prostate biopsy performed for rising prostate-specific antigen (PSA) levels after prostate radiation. MATERIALS AND METHODS: We performed a retrospective review of 238 prostate cancer patients with a negative biopsy following definitive radiotherapy. Seventy-five of these patients had biochemical recurrence at the time of biopsy. A negative biopsy was defined as the absence of prostate cancer without radiation-treatment effect in the specimen. RESULTS: Patients underwent biopsy at a mean of 41 months after the completion of radiation. They had a mean PSA of 6. Patients were followed for an average of 63 months. Thirty-two patients (43%) developed metastasis, and 11 (15%) died of prostate cancer despite a negative post-radiation biopsy. Five of nine patients (56%) with sequential biopsies had a positive second biopsy. CONCLUSIONS: Patients with PSA recurrence and a negative post-radiation biopsy have a high chance of persistent local disease, progression, and death from prostate cancer. Furthermore, an initial negative biopsy does not rule-out local recurrence. Patients with biochemical recurrence after radiotherapy for prostate cancer need to be evaluated earlier for local recurrence.

G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences

Abstract: G*Power (Erdfelder, Faul, & Buchner, 1996) was designed as a general stand-alone power analysis program for statistical tests commonly used in social and behavioral research. G*Power 3 is a major extension of, and improvement over, the previous versions. It runs on widely used computer platforms (i.e., Windows XP, Windows Vista, and Mac OS X 10.4) and covers many different statistical tests of thet, F, and χ2 test families. In addition, it includes power analyses forz tests and some exact tests. G*Power 3 provides improved effect size calculators and graphic options, supports both distribution-based and design-based input modes, and offers all types of power analyses in which users might be interested. Like its predecessors, G*Power 3 is free.

A power primer.

Abstract: One possible reason for the continued neglect of statistical power analysis in research in the behavioral sciences is the inaccessibility of or difficulty with the standard material. A convenient, although not comprehensive, presentation of required sample sizes is provided here. Effect-size indexes and conventional values for these are given for operationally defined small, medium, and large effects. The sample sizes necessary for .80 power to detect effects at these levels are tabled for eight standard statistical tests: (a) the difference between independent means, (b) the significance of a product-moment correlation, (c) the difference between independent rs, (d) the sign test, (e) the difference between independent proportions, (f) chi-square tests for goodness of fit and contingency tables, (g) one-way analysis of variance, and (h) the significance of a multiple or multiple partial correlation.

Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses.

Abstract: G*Power is a free power analysis program for a variety of statistical tests. We present extensions and improvements of the version introduced by Faul, Erdfelder, Lang, and Buchner (2007) in the domain of correlation and regression analyses. In the new version, we have added procedures to analyze the power of tests based on (1) single-sample tetrachoric correlations, (2) comparisons of dependent correlations, (3) bivariate linear regression, (4) multiple linear regression based on the random predictor model, (5) logistic regression, and (6) Poisson regression. We describe these new features and provide a brief introduction to their scope and handling.

Experimental Design and Data Analysis for Biologists

Abstract: An essential textbook for any student or researcher in biology needing to design experiments, sample programs or analyse the resulting data The text begins with a revision of estimation and hypothesis testing methods, covering both classical and Bayesian philosophies, before advancing to the analysis of linear and generalized linear models Topics covered include linear and logistic regression, simple and complex ANOVA models (for factorial, nested, block, split-plot and repeated measures and covariance designs), and log-linear models Multivariate techniques, including classification and ordination, are then introduced Special emphasis is placed on checking assumptions, exploratory data analysis and presentation of results The main analyses are illustrated with many examples from published papers and there is an extensive reference list to both the statistical and biological literature The book is supported by a website that provides all data sets, questions for each chapter and links to software

Mediation in experimental and nonexperimental studies: New procedures and recommendations.

Abstract: Mediation is said to occur when a causal effect of some variable X on an outcome Y is explained by some intervening variable M. The authors recommend that with small to moderate samples, bootstrap methods (B. Efron & R. Tibshirani, 1993) be used to assess mediation. Bootstrap tests are powerful because they detect that the sampling distribution of the mediated effect is skewed away from 0. They argue that R. M. Baron and D. A. Kenny's (1986) recommendation of first testing the X --> Y association for statistical significance should not be a requirement when there is a priori belief that the effect size is small or suppression is a possibility. Empirical examples and computer setups for bootstrap analyses are provided.