Validation of prognostic indices using the frailty model

Concordance measures in shared frailty models: application to clustered data in cancer prognosis

Frailty models are gaining interest in prognostic studies, especially because of the spread of multicenter studies. However, little research has been performed to extend prognostic tools to frailty models, including discrimination measures. As previously performed for the Harrell's c-index, we extended two different discrimination measures (the model-based concordance probability estimation of Gönen and Heller and the nonparametric Uno's c-index) to take into account cluster membership. We calculate measures at three levels: between-group, where only patients with different frailties are compared, within-group, where only patients sharing the same frailty are compared, and overall. We performed simulations to study the impact of group size and the number of groups on these measures. Results showed that the two measures can be extended to frailty models while remaining independent from censoring distribution, provided that the group size is sufficient. We apply the extended measures to two real datasets, a meta-analysis and a large multicenter trial.

Reconstructive urology and geriatrics: issues in older adults

PURPOSE OF REVIEW

The elderly population is continuing to expand at record pace in the vast majority of countries worldwide. Many urologic conditions that necessitate reconstructive surgery occur in geriatric patients. To date, there has been a paucity of research on the effects of aging with regard to reconstructive procedures in elderly patients. This review examines factors that influence the feasibility and outcomes of reconstructive urologic surgery in older adults.

RECENT FINDINGS

Age alone has generally not been identified as a significant predictive factor for outcomes in geriatric patients undergoing surgery. Comorbid diseases associated with reduction of physiologic reserve capacity and impairments in the level of independence for activities of daily living appear to have more predictive value. Recent research has focused on defining frailty as a condition that frequently occurs in older adults and may influence clinical outcomes. A variety of cellular and tissue changes associated with aging have also been studied. Inflammatory mediators may play an important role in this process.

SUMMARY

Many urologic conditions that require reconstructive surgery occur in elderly patients. Careful planning may help to improve outcomes. However, there appear to be inherent changes associated with the physiology of normal aging that can significantly influence this process.