Sam Wieand
University of Pittsburgh
Publications 20
#1John BryantH-Index: 48
#2Walter M. CroninH-Index: 17
Last.Sam Wieand (University of Pittsburgh)H-Index: 12
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The chapter deals with multicenter clinical trials, which are defined as studies involving two or more field sites conducted according to a common protocol that uses a single data coordinating center to receive, process, and analyze study data. Several examples are provided. Organizational, structural, and analytic aspects of trials, and guidelines for the conduct of such studies are discussed. Keywords: multicenter trials; clinical trials
#1Mary Claire King (UW: University of Washington)H-Index: 91
#2Sam Wieand (University of Pittsburgh)H-Index: 12
Last.Bernard Fisher (University of Pittsburgh)H-Index: 100
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ContextAmong cancer-free women aged 35 years or older, tamoxifen reduced the incidence of estrogen receptor (ER)–positive but not ER-negative breast cancer. The effect of tamoxifen on breast cancer incidence among women at extremely high risk due to inheritedBRCA1 or BRCA2mutations is unknown.ObjectiveTo evaluate the effect of tamoxifen on incidence of breast cancer among cancer-free women with inherited BRCA1 or BRCA2 mutations.Design, Setting, and ParticipantsGenomic analysis of BRCA1 and BRCA...
601 CitationsSource
#1Norman WolmarkH-Index: 117
#2Linda H. ColangeloH-Index: 24
Last.Sam WieandH-Index: 12
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Abstract During the last decade, the National Surgical Adjuvant Breast and Bowel Project (NSABP) has completed six adjuvant chemotherapy trials comparing different adjuvant therapy regimens or adjuvant therapy versus surgery alone. A seventh trial is ongoing. These trials have contributed to defining the role of adjuvant therapy in colon cancer. Patients eligible for inclusion in NSABP trials had been diagnosed as having stage II or III colon cancer with no evidence of gross residual or metastat...
32 CitationsSource
#1Birol Emir (Bayer)H-Index: 21
#2Sam Wieand (University of Pittsburgh)H-Index: 12
Last.Zhiliang Ying (RU: Rutgers University)H-Index: 46
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In this paper we study a class of non-parametric statistics for comparing diagnostic markers with repeated measurements. Using adapted definitions of specificity and sensitivity, we suggest methods to compare the average of sensitivities across all specificities or a range of specificities. The theory allows for correlations introduced by the fact that markers may be obtained from the same patient at multiple visits and that both markers being compared may be obtained from the same patient. Resu...
18 CitationsSource
#1Norman WolmarkH-Index: 8
#2Howard E. RocketteH-Index: 53
Last.Bernard FisherH-Index: 100
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PURPOSE: To compare the efficacy of leucovorin-modulated fluorouracil (FU+LV) with that of fluorouracil and levamisole (FU+LEV) or with the combination of FU+LV and levamisole (FU+LV+LEV). PATIENTS AND METHODS: Between July 1989 and December 1990, 2,151 patients with Dukes' B (stage II) and Dukes' C (stage III) carcinoma of the colon were entered onto National Surgical Adjuvant Breast and Bowl Project protocol C-04. Patients were randomly assigned to receive FU+LV (weekly regimen), FU + LEV, or ...
396 CitationsSource
#1Sin-Ho Jung (IU: Indiana University)H-Index: 45
#2Sam Wieand (University of Pittsburgh)H-Index: 12
If the proportional hazards model (PHM) holds, the regression coefficients for t-year survival probability using the log-log link are equal to those of Cox's PHM with reverse sign for any time point t. In this article, the goodness-of-fit of Cox's model is checked by fitting the log-log regression models at different values of t and plotting the coefficient estimates against t.
1 CitationsSource
#1Birol Emir (Bayer)H-Index: 21
#2Sam Wieand (University of Pittsburgh)H-Index: 12
Last.Steve Cha (Mayo Clinic)H-Index: 3
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We consider methods for evaluating repeated markers to be used as a substitute for a clinical examination or to predict an outcome, in our case progression of breast cancer. We propose a definition of specificity and sensitivity for this setting and describe non-parametric estimators for these parameters. We then derive the theory required to obtain confidence intervals for the specificity and sensitivity of a marker and to define an asymptotically normal statistic for comparing the sensitivitie...
36 CitationsSource
PURPOSE: National Surgical Adjuvant Breast and Bowel Project Protocol R-03 was designed to determine the worth of preoperative chemotherapy and radiation therapy in the management of operable rectal cancer. METHODS: Thus far, 116 patients of an eventual 900 with primary operable rectal cancer have been randomized to receive multimodality therapy to begin preoperatively (59 patients) or identical therapy beginning after curative surgery (57). All patients received seven cycles of 5-fluorouracil (...
319 CitationsSource
#1Stewart J. AndersonH-Index: 58
#2Bernard FisherH-Index: 100
Last.Sam WieandH-Index: 12
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#1Sin-Ho Jung (Mayo Clinic)H-Index: 45
#2Sam Wieand (Mayo Clinic)H-Index: 12
Last.Stephen S. Cha (Mayo Clinic)H-Index: 55
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A proliferation of biologic markers has led to increased interest in methods for comparing the prognostic value of markers in predicting time to recurrence of or death from disease. This paper proposes a non-parametric test statistic for comparing two continuous markers when the outcome of interest is time to an event and the outcome is subject to right censoring. Results from Monte Carlo studies show that the new testing procedure is reliable for practical use. We present an example in which we...
8 CitationsSource