scholarly journals New goodness-of-fit test for exponentiality based on a conditional moment characterisation

ORiON ◽  
2019 ◽  
Vol 35 (2) ◽  
pp. 145-160
Author(s):  
M Smuts ◽  
JS Allison ◽  
L Santana
Keyword(s):  
Exponential Distribution ◽  
Queuing Theory ◽  
Goodness Of Fit ◽  
Proportional Hazards Model ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
Real World Data ◽  
Conditional Moment ◽  
Goodness Of Fit Test ◽  
Underlying Assumption

The exponential distribution plays a key role in the practical application of reliability theory, survival analysis, engineering and queuing theory. These applications often rely on the underlying assumption that the observed data originate from an exponential distribution. In this paper, two new tests for exponentiality are proposed, which are based on a conditional second moment characterisation. The proposed tests are compared to various established tests for exponentiality by means of a simulation study where it is found that the new tests perform favourably relative to the existing tests. The tests are also applied to real-world data sets with independent and identically distributed data as well as to simulated data from a Cox proportional hazards model, to determine whether the residuals obtained from the fitted model follow a standard exponential distribution.

scholarly journals Multiple immune-related adverse events and anti-tumor efficacy: real-world data on various solid tumors

2020 ◽  
Author(s):  
Keitaro Shimozaki ◽  
Yasutaka Sukawa ◽  
Noriko Beppu ◽  
Isao Kurihara ◽  
Shigeaki Suzuki ◽  
...  
Keyword(s):  
Retrospective Study ◽  
Adverse Events ◽  
Real World ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Checkpoint Inhibitors ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
University Hospital ◽  
Real World Data

Abstract Background Immune checkpoint inhibitors have been approved for various types of cancer; however, they cause a broad spectrum of immune-related adverse events (irAEs). The association between the development of irAEs and the clinical benefit remains uncertain. We aimed to evaluate the association of irAEs and the treatment efficacy in the real-world practice. Methods We conducted a retrospective study on patients with recurrent or metastatic non-small cell lung cancer, melanoma, renal cell carcinoma, or gastric cancer who received anti-PD-1/PD-L1 antibodies (nivolumab, pembrolizumab, or atezolizumab) at the Keio University Hospital between September 2014 and January 2019. We recorded treatment-related AEs from medical records and graded them using the Common Terminology Criteria for Adverse Events version 4. We performed an overall survival (OS) analysis using a Cox proportional hazards model. Results Among 212 patients eligible for this study, 108 experienced irAEs and 42 developed multiple irAEs. OS in patients with multiple irAEs was significantly longer than that in patients with single irAE (42.3 months vs. 18.8 months; hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.25–0.93; P = 0.03). Moreover, OS from the development of a second irAE in those with multiple irAEs was longer than that from the development of the first irAE in patients with single irAEs (median OS, 26.9 months vs. 17.7 months, respectively; HR, 0.59; 95% CI, 0.30–1.14; P = 0.11). Conclusions Our single-center retrospective study revealed a remarkable tendency associating the development of multiple irAEs with favorable prognoses.

Comparative effectiveness of nab-paclitaxel plus gemcitabine versus FOLFIRINOX in metastatic pancreatic cancer: A nationwide chart review in the United States.

2018 ◽  
Vol 36 (4_suppl) ◽  
pp. 376-376
Author(s):  
Sunnie S. Kim ◽  
James Signorovitch ◽  
Hongbo Yang ◽  
Oscar Patterson-Lomba ◽  
Cheryl Xiang ◽  
...  
Keyword(s):  
Real World ◽  
Medical Records ◽  
Proportional Hazards Model ◽  
Specific Treatment ◽  
The United States ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
Real World Data ◽  
Significant Difference ◽  
Treatment Sequences

376 Background: nab-Paclitaxel plus gemcitabine ( nab-P+G) and FOLFIRINOX (FFX) are among the most common first-line (1L) therapies for metastatic adenocarcinoma of the pancreas (mPC), yet there is no head-to-head trial comparing their efficacy and real-world data is limited. As new second-line (2L) therapies become available, it is important to understand the real-world effectiveness associated with different treatment sequences. Methods: This retrospective cohort study compared the efficacy and safety of 1L nab-P+G vs. FFX, overall and under specific treatment sequences. Medical records were reviewed by 215 physicians across the US who provided information for mPC patients who initiated 1L with nab-P+G or FFX between 04/01/2015-12/31/2015. The outcomes of interest were overall survival (OS) and tolerability. OS was evaluated using Kaplan-Meier curves, and compared between cohorts using Cox proportional hazards model adjusting for baseline characteristics. Results: Medical records were reviewed for 654 patients receiving nab-P+G (n = 337) or FFX (n = 317) as 1L therapy for mPC. Patients in the nab-P+G cohort were older, less likely to have ECOG ≤ 1 and had more comorbidities than patients in the FFX cohort. There was no statistically significant difference in OS (adjusted HR = 0.99, p = 0.96), with median OS (mOS) being 12.1 and 13.8 months for nab-P+G and FFX, respectively. Among the subgroup of patients with ECOG ≤ 1, mOS was 14.1 and 13.7 months, respectively (adjusted HR = 1.00, p = 0.99). Among patients with 1L nab-P+G and FFX, 36.1% and 41.3% received 2L therapy and experienced mOS of 16.3 and 16.6 months, respectively (HR = 1.04, p = 0.76). Among commonly observed adverse events (AEs) (≥ 5% of patients in both cohorts), the rates of diarrhea, fatigue, mucositis, nausea and vomiting were higher in the FFX than nab-P+G cohort (all p < 0.05). Conclusions: In a nationwide sample of mPC patients, real-world survival outcomes were similar between patients receiving 1L nab-P+G or FFX. both overall and among patients who went on to receive active 2L treatments. In addition, nab-P+G was associated with significantly lower rates of common AEs compared with FFX.

scholarly journals Cox Proportional Hazards Model for Identification of the Prognostic Factors in the Survival of Acute Liver Failure Patients in India

2018 ◽  
Vol 2 ◽  
pp. 53-74
Author(s):  
Shankar Prasad Khanal ◽  
V. Sreenivas ◽  
S.K. Acharya
Keyword(s):  
Survival Analysis ◽  
Prognostic Factors ◽  
Liver Failure ◽  
Cerebral Edema ◽  
Goodness Of Fit ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
Hazards Model

Background: Acute Liver Failure (ALF) is a kind of dangerous rare liver injury among all liver diseases. Different statistical methods such as Logistic regression, Kaplan-Meier estimate of survival function followed by Log-rank test and semi-parametric approaches of survival analysis has been applied in order to identify the significant risk factors of ALF patients. In most of the studies, regression models used in this setup has not been evaluated by model assumptions and their goodness of fit tests.Objective: To apply appropriate survival analysis technique to identify the prognostic factors in the survival of ALF patients, to develop prognostic index, and to predict survival probability for different scenario.Materials and Methods: The study is based on the retrospective cohort study design with altogether 1099 ALF patients taken from the liver clinic, All India Institute of Medical Sciences, New Delhi India. Cox regression has been considered as the suitable model for handling this time to event data, and the assumptions of the model, goodness of fit of the model was assessed and survival probabilities were predicted.Results: This study has identified six prognostic factors namely age, prothrombin time, cerebral edema, total serum bilirubin, serum creatinine and etiology for ALF patients. The hazards of mortality [HR: 2.38; 95% C.I.: (1.99, 2.85), p < 0.001] is the highest for cerebral edema among all these prognostic factors. Nearly 9%, 26%, 39%, 50%, 59% and 63% of ALF patients with a PI of 1, 3, 5, 7, 9 and 10 respectively die by 3 days of hospital stay.Conclusion: The developed Cox Proportional Hazards model with six prognostic factors has satisfied the model assumptions and goodness of fit tests. The risk score and the predicted survival probabilities will be immensely helpful to the hepatologists to make a quick decision regarding the likely prognosis of a patient at admission and helpful in triaging the ALF patients for liver transplant.Nepalese Journal of Statistics, Vol. 2, 53-74

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