Clinical trials : journal of the Society for Clinical Trials
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Recently, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial published 7-year complete prostate cancer mortality results, which showed no benefit of screening with prostate specific antigen (PSA) and digital rectal examination (DRE). An issue of concern was the substantial level of 'contamination', or use of PSA and DRE in control arm men. ⋯ Use of prostate screening by control arm men was substantial, but also substantially less than in screened arm men. Detailed quantitative analyses of screening use across arms are critical for understanding current and future findings from the prostate component of PLCO.
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The aim was to compare simple imputation, multiple imputation, and modeling approaches to deal with 'missing' quality of life data. Data were obtained from five clinical trials, which employed a reminder system for follow-up questionnaires. Previous studies have compared imputation strategies by artificially removing data according to prespecified mechanisms. Our approach differs from previous study as actual collected data are utilized. ⋯ Multiple imputation is recommended for missing quality of life data as it makes the assumption of missing at random which in the quality of life setting is more plausible than the assumption of missing completely at random for which most simple imputation methods are based. Pattern mixture models can be complex and did not perform well in this setting.