PubMed · 15849282
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P McCrory. 2005. A cause for concern?. https://pubmed.ncbi.nlm.nih.gov/15849282/
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Longitudinal models are commonly used for studying data collected on individuals repeatedly through time. While there are now a variety of such models available (marginal models, mixed effects models, etc.), far fewer options exist for the closely related issue of variable selection. In addition, longitudinal data typically derive from medical or other large-scale studies where often large numbers of potential explanatory variables and hence even larger numbers of candidate models must be considered. Cross-validation is a popular method for variable selection based on the predictive ability of the model. Here, we propose a cross-validation Markov chain Monte Carlo procedure as a general variable selection tool which avoids the need to visit all candidate models. Inclusion of a 'one-standard error' rule provides users with a collection of good models as is often desired. We demonstrate the effectiveness of our procedure both in a simulation setting and in a real application.
Prostate cancer remains a most intriguing condition, which poses unique challenges. On reviewing recent literature on localised disease (confined within the capsule T1 or T2, N0, M0), it would seem that it is over treated, resulting in significant morbidity. We now have strong evidence, however, that there can be mortality associated with 'watchful waiting'. Clinicians should, therefore, aim to identify men at risk of progression in order that they should be treated effectively with minimal adverse effects. In this paper, we report on recent developments in the expanding array of management options available.
BACKGROUND: Urachal carcinoma (UrC) is a rare malignancy, and patients with this disease have a poor prognosis. In this article, the authors report 50 years of experience with this tumor at the Mayo Clinic. METHODS: A urachal mass was described in 130 patients, and 66 of those masses were malignant. The authors identified multivariate predictors of malignancy in clinically diagnosed urachal masses and predictors of UrC-specific survival. This report presents a novel 4-category staging system for UrC along with the treatment history of this tumor and the results of salvage therapy. RESULTS: Twenty women and 46 men were identified with UrC. The strongest predictors of malignancy in a urachal mass were hematuria and age older than 55 years. The 5-year cancer-specific survival rate was 49%. The new Mayo staging system was less complicated than the Sheldon system, although both systems predicted cancer-specific mortality equally well. Positive surgical margins (hazard ratio [HR], 4.7), high tumor grade (HR, 3.6), positive local lymph nodes (HR, 5.1), metastases at diagnosis (HR, 3.3), advanced tumor stage (HR, 4.8), failure to perform umbilectomy (HR, 3.0), and primary radiation therapy (HR, 2.9) were all univariately associated with death (P <.05). Only grade and margins were significant in the multivariate analysis. No survival benefit was noted for lymphadenectomy or adjuvant therapy. Salvage surgery resulted in a long-term cure for 50% of patients who had local recurrences. No effective treatment was identified for patients with metastatic UrC. CONCLUSIONS: Early and complete extended partial cystectomy, including umbilectomy, is critical to the survival of patients with UrC. The authors recommend using the Mayo staging system in future studies because of its simplicity. The current results indicated that the most important predictors of prognosis were tumor grade and surgical margin status.