Analysis of Biased Survival Data: The Canadian Study of Health and Aging andbeyond

2014 ◽  
pp. 217-232
Keyword(s):  
Survival Data ◽  
Canadian Study

The Effect of Partly Missing Covariates on Statistical Power in Randomized Controlled Trials With Discrete-Time Survival Endpoints

Methodology ◽  
2017 ◽  
Vol 13 (2) ◽  
pp. 41-60
Author(s):  
Shahab Jolani ◽  
Maryam Safarkhani
Keyword(s):  
Randomized Controlled Trials ◽  
Discrete Time ◽  
Treatment Effect ◽  
Survival Data ◽  
Controlled Trials ◽  
Missing Covariates ◽  
Indicator Method ◽  
Imputation Methods ◽  
Randomized Controlled ◽  
Baseline Covariates

Abstract. In randomized controlled trials (RCTs), a common strategy to increase power to detect a treatment effect is adjustment for baseline covariates. However, adjustment with partly missing covariates, where complete cases are only used, is inefficient. We consider different alternatives in trials with discrete-time survival data, where subjects are measured in discrete-time intervals while they may experience an event at any point in time. The results of a Monte Carlo simulation study, as well as a case study of randomized trials in smokers with attention deficit hyperactivity disorder (ADHD), indicated that single and multiple imputation methods outperform the other methods and increase precision in estimating the treatment effect. Missing indicator method, which uses a dummy variable in the statistical model to indicate whether the value for that variable is missing and sets the same value to all missing values, is comparable to imputation methods. Nevertheless, the power level to detect the treatment effect based on missing indicator method is marginally lower than the imputation methods, particularly when the missingness depends on the outcome. In conclusion, it appears that imputation of partly missing (baseline) covariates should be preferred in the analysis of discrete-time survival data.

Sex Differences in Neuropathy and Neuropathic Pain in Long-Standing Diabetes—Results from the Canadian Study of Longevity in Type 1 Diabetes

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 560-P
Author(s):  
NANCY CARDINEZ ◽  
LEIF ERIK LOVBLOM ◽  
JOHNNY-WEI BAI ◽  
ALON ABRAHAM ◽  
EVAN J. LEWIS ◽  
...  
Keyword(s):  
Type 1 Diabetes ◽  
Sex Differences ◽  
Neuropathic Pain ◽  
Canadian Study

Gamma Knife surgery combined with resection for treatment of a single brain metastasis: preliminary results

2010 ◽  
Vol 113 (Special_Supplement) ◽  
pp. 90-96 ◽  
Author(s):  
M. Yashar S. Kalani ◽  
Aristotelis S. Filippidis ◽  
Maziyar A. Kalani ◽  
Nader Sanai ◽  
David Brachman ◽  
...  
Keyword(s):  
Survival Data ◽  
Initial Treatment ◽  
Median Survival Time ◽  
Local Tumor Control ◽  
Survival Duration ◽  
Tumor Control ◽  
Local Tumor ◽  
Systemic Control ◽  
Cranial Metastasis

Object Resection and whole-brain radiation therapy (WBRT) have classically been the standard treatment for a single metastasis to the brain. The objective of this study was to evaluate the use of Gamma Knife surgery (GKS) as an alternative to WBRT in patients who had undergone resection and to evaluate patient survival and local tumor control. Methods The authors retrospectively reviewed the charts of 150 patients treated with a combination of stereotactic radiosurgery and resection of a cranial metastasis at their institution between April 1997 and September 2009. Patients who had multiple lesions or underwent both WBRT and GKS were excluded, as were patients for whom survival data beyond the initial treatment were not available. Clinical and imaging follow-up was assessed using notes from clinic visits and MR imaging studies when available. Follow-up data beyond the initial treatment and survival data were available for 68 patients. Results The study included 37 women (54.4%) and 31 men (45.6%) (mean age 60 years, range 28–89 years). In 45 patients (66.2%) there was systemic control of the primary tumor when the cranial metastasis was identified. The median duration between resection and radiosurgery was 15.5 days. The median volume of the treated cavity was 10.35 cm3 (range 0.9–45.4 cm3), and the median dose to the cavity margin was 15 Gy (range 14–30 Gy), delivered to the 50% isodose line (range 50%–76% isodose line). The patients' median preradiosurgery Karnofsky Performance Scale (KPS) score was 90 (range 40–100). During the follow-up period we identified 27 patients (39.7%) with recurrent tumor located either local or distant to the site of treatment. The median time from primary treatment of metastasis to recurrence was 10.6 months. The patients' median length of survival (interval between first treatment of cerebral metastasis and last follow-up) was 13.2 months. For the patient who died during follow-up, the median time from diagnosis of cerebral metastasis to death was 11.5 months. The median duration of survival from diagnosis of the primary cancer to last follow-up was 30.2 months. Patients with a pretreatment KPS score ≥ 90 had a median survival time of 23.2 months, and patients with a pretreatment KPS score < 90 had a median survival time of 10 months (p < 0.008). Systemic control of disease at the time of metastasis was not predictive of increased survival duration, although it did tend to improve survival. Conclusions Although the debate about the ideal form of radiation treatment after resection continues, these findings indicate that GKS combined with surgery offers comparable survival duration and local tumor control to WBRT for patients with a diagnosis of a single metastasis.

Gamma Knife surgery for the treatment of melanoma metastases: the effect of intratumoral hemorrhage on survival

2008 ◽  
Vol 109 (Supplement) ◽  
pp. 99-105 ◽  
Author(s):  
Andy J. Redmond ◽  
Michael L. DiLuna ◽  
Ryan Hebert ◽  
Jennifer A. Moliterno ◽  
Rani Desai ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Survival Data ◽  
Tumor Burden ◽  
Gamma Knife Surgery ◽  
Survival Sex ◽  
Whole Brain Radiation ◽  
Melanoma Metastases ◽  
History Of ◽  
Independent Association ◽  
Intratumoral Bleeding

Object Gamma Knife surgery (GKS) improves overall survival in patients with malignant melanoma metastatic to the brain. In this study the authors investigated which patient- or treatment-specific factors influence survival of patients with melanoma brain metastases; they pay particular interest to pre- and post-GKS hemorrhage. Methods Demographic, treatment, and survival data on 59 patients with a total of 208 intracranial metastases who underwent GKS between 1998 and 2007 were abstracted from treatment records and from the Connecticut Tumor Registry. Multivariate analysis was used to identify factors that independently affected survival. Results Survival was significantly better in patients with solitary metastasis (p = 0.04), lesions without evidence of pre-GKS hemorrhage (p = 0.004), and in patients with total tumor volume treated < 4 cm3 (p = 0.02). Intratumoral bleeding occurred in 23.7% of patients pre-GKS. Intratumoral bleeding occurred at a mean of 1.8 months post-GKS at a rate of 15.2%. Unlike the marked effect of pretreatment bleeding, posttreatment bleeding did not independently affect survival. Sex, systemic control, race, metastases location, whole-brain radiation therapy, chemotherapy, history of antithrombotic medications, and cranial surgery had no independent association with survival. Conclusions These data corroborate previous findings that tumor burden (either as increased number or total volume of lesions) at the time of GKS is associated with diminished patient survival in those with intracerebral melanoma metastases. Patients who were noted to have hemorrhagic melanoma metastases prior to GKS appear to have a worse prognosis following GKS compared with patients with nonhemorrhagic metastases, despite similar rates of bleeding pre- and post-GKS treatment. Gamma Knife surgery itself does not appear to increase the rate of hemorrhage.

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