Parental Survival Data: Some Results of the Application of Ledermann's Model Life Tables

1976 ◽  
Vol 30 (1) ◽  
pp. 59
Author(s):  
H. J. Page ◽  
G. Wunsch
Keyword(s):  
Survival Data ◽  
Life Tables

Estimating Housing Mortality with Standard Loss Curves

1986 ◽  
Vol 18 (11) ◽  
pp. 1521-1530 ◽  
Author(s):  
M E Gleeson
Keyword(s):  
Survival Data ◽  
Statistical Models ◽  
Life Tables ◽  
Time To Failure ◽  
Truncated Data ◽  
Mobile Homes ◽  
Analytical Work ◽  
Tests Of Fit

Tests of fit using one set of data on mobile homes and another on conventional housing indicate that standard loss curves, such as the Pearl-Reed and Weibull curves, can be used to approximate housing survivorship functions. This finding opens up the possibility of analytical work using standard curves and the application of time-to-failure statistical models that are based on such curves. Tests of fit of standard curves to the two housing survivorship functions using truncated data are also encouraging, suggesting means of estimating housing mortality and computing life tables with incomplete cohort survival data.

A comparison of time-specific and cohort-specific life tables for Belding's ground squirrels, Spermophilus beldingi

1986 ◽  
Vol 64 (3) ◽  
pp. 602-605 ◽  
Author(s):  
Richard M. Zammuto ◽  
Paul W. Sherman
Keyword(s):  
Life Table ◽  
Survival Data ◽  
Life Tables ◽  
Ground Squirrels ◽  
Age Classes ◽  
Free Living ◽  
Female Population ◽  
Spermophilus Beldingi ◽  
Time Specific ◽  
Combined Data

Eight years of age-specific survival data and 6 years of fecundity data from a free-living population of Belding's ground squirrels (Spermophilus beldingi) at Tioga Pass, California, were used to test the hypothesis that time-specific life tables, based on data from individual years, were different from the cohort-specific life table, based on the combined data from all years. The results indicated that neither the age structure of the male nor the female population significantly differed among years (all P > 0.05). Furthermore, the means and the variances in the sizes of weaned litters did not differ among years either in the population at large or within individual age-classes (all P > 0.05). A 27-day snowstorm that occurred in the spring of 1977 increased mortality and reduced reproduction, but it did not change the ground squirrels' age-specific survival or fecundity patterns. Taken together, our analyses revealed that each time-specific life table provided age-specific survival and fecundity estimates that were statistically indistinguishable (P > 0.05) from the composite, cohort-specific life table for each sex, regardless of severe environmental conditions. This is the first demonstration of the equivalence of time- and cohort-specific life tables for a free-living population of mammals.

LIFE TABLES AND INTRINSIC RATES OF INCREASE OF APTEROUS BLACK BEAN APHIDS AND PEA APHIDS, ON BROAD BEAN (HOMOPTERA: APHIDIDAE)

1972 ◽  
Vol 104 (11) ◽  
pp. 1717-1722 ◽  
Author(s):  
B. D. Frazer
Keyword(s):  
Survival Data ◽  
Acyrthosiphon Pisum ◽  
Broad Bean ◽  
Aphid Species ◽  
Natural Increase ◽  
Life Tables ◽  
Pea Aphid ◽  
Aphis Fabae ◽  
Black Bean ◽  
Pea Aphids

AbstractLife tables were prepared from daily fecundity and survival data on 69 apterous black bean aphids, Aphis fabae Scopoli, and 47 apterous pea aphids, Acyrthosiphon pisum (Harris). Both were on broad beans in 20° ± 0.5 °C, 70–80% R.H., and 16 hr light per day. The intrinsic rates of natural increase (rm) computed from the life tables were 0.359 ♀/♀ day for the bean aphid and 0.404 ♀/♀ day for the pea aphid. Mortality was not important in determining the rates of increase because very few aphids died during their reproductive periods. Only 5 of 116 reproducing aphids died, all from inability to extrude nymphs which had died before bursting their embryonic membranes. These nymphs became covered with a discharge from the mother which cemented them in place and prevented the birth of succeeding nymphs. The resulting engorged females died in 3–4 days.An analysis of and comparison with life tables of two other aphid species in addition to those produced here showed that the differences in rm were due almost entirely to differences in fecundity. Two fecundity patterns, correlated with aphid phylogeny, were recognized.

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.

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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