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Hypertabastic survival model.

Tabatabai MA, Bursac Z, Williams DK, Singh KP - Theor Biol Med Model (2007)

Bottom Line: We then demonstrate the application of the hypertabastic survival model by applying it to data from two motivating studies.The first one demonstrates the proportional hazards version of the model by applying it to a data set from multiple myeloma study.Based on the results from the simulation study and two applications, the proposed model shows to be a flexible and promising alternative to practitioners in this field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR, USA. mtabatabai@cameron.edu

ABSTRACT
A new two-parameter probability distribution called hypertabastic is introduced to model the survival or time-to-event data. A simulation study was carried out to evaluate the performance of the hypertabastic distribution in comparison with popular distributions. We then demonstrate the application of the hypertabastic survival model by applying it to data from two motivating studies. The first one demonstrates the proportional hazards version of the model by applying it to a data set from multiple myeloma study. The second one demonstrates an accelerated failure time version of the model by applying it to data from a randomized study of glioma patients who underwent radiotherapy treatment with and without radiosensitizer misonidazole. Based on the results from the simulation study and two applications, the proposed model shows to be a flexible and promising alternative to practitioners in this field.

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a) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy with radiosentisizer misonidazole for glioma brain cancer; b) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy without radiosentisizer misonidazole for glioma brain cancer.
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Figure 7: a) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy with radiosentisizer misonidazole for glioma brain cancer; b) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy without radiosentisizer misonidazole for glioma brain cancer.

Mentions: Using AIC, we came to the conclusion that both Weibull and hypertabastic models fit the data very well. However, the Weibull AIC value was 75.54 which indicates the best fit. For the hypertabastic model, the AIC value was 76.72 which was slightly less than Weibull. The remaining AIC values for log-normal, log-logistic and Cox are 79.15, 78.45, and 107.43 respectively. At the median age of 49, the median survival time for those patients who underwent radiotherapy with radiosensitizer misonidazole using the hypertabastic, Weibul, log-normal, log-logistic, and the Cox models are 289, 316, 270, 277, and 244 days respectively. The corresponding median survival times for the group without the radiosensitizer misonidazole are 449, 453, 423, 456, and 488 days respectively. By examining the Kaplan-Meier survival functions for the two groups we observe the crossing pattern which is a clear indication of violation of proportional hazards assumption. Figures 6a and 6b show the graphs of hypertabastic hazard and survival functions for both treatment groups at the age level of 49. The hazards for both groups are increasing function of time. For those patients who received radiotherapy treatment with radiosensitizer misonidazole, hazard function reached its maximum velocity in about 200 days. For those who did receive radiotherapy without misonidazole, hazard function reached its maximum velocity in about 311 days. These are the points in time where the speeds of failure rates (hazards) are highest (Figure 6c). Figures 7a and 7b represent 3-dimensional graphs of survival by time and age for each treatment group separately.


Hypertabastic survival model.

Tabatabai MA, Bursac Z, Williams DK, Singh KP - Theor Biol Med Model (2007)

a) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy with radiosentisizer misonidazole for glioma brain cancer; b) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy without radiosentisizer misonidazole for glioma brain cancer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2169222&req=5

Figure 7: a) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy with radiosentisizer misonidazole for glioma brain cancer; b) Hypertabastic 3D survival curve with variables time and age for group using radiotherapy without radiosentisizer misonidazole for glioma brain cancer.
Mentions: Using AIC, we came to the conclusion that both Weibull and hypertabastic models fit the data very well. However, the Weibull AIC value was 75.54 which indicates the best fit. For the hypertabastic model, the AIC value was 76.72 which was slightly less than Weibull. The remaining AIC values for log-normal, log-logistic and Cox are 79.15, 78.45, and 107.43 respectively. At the median age of 49, the median survival time for those patients who underwent radiotherapy with radiosensitizer misonidazole using the hypertabastic, Weibul, log-normal, log-logistic, and the Cox models are 289, 316, 270, 277, and 244 days respectively. The corresponding median survival times for the group without the radiosensitizer misonidazole are 449, 453, 423, 456, and 488 days respectively. By examining the Kaplan-Meier survival functions for the two groups we observe the crossing pattern which is a clear indication of violation of proportional hazards assumption. Figures 6a and 6b show the graphs of hypertabastic hazard and survival functions for both treatment groups at the age level of 49. The hazards for both groups are increasing function of time. For those patients who received radiotherapy treatment with radiosensitizer misonidazole, hazard function reached its maximum velocity in about 200 days. For those who did receive radiotherapy without misonidazole, hazard function reached its maximum velocity in about 311 days. These are the points in time where the speeds of failure rates (hazards) are highest (Figure 6c). Figures 7a and 7b represent 3-dimensional graphs of survival by time and age for each treatment group separately.

Bottom Line: We then demonstrate the application of the hypertabastic survival model by applying it to data from two motivating studies.The first one demonstrates the proportional hazards version of the model by applying it to a data set from multiple myeloma study.Based on the results from the simulation study and two applications, the proposed model shows to be a flexible and promising alternative to practitioners in this field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR, USA. mtabatabai@cameron.edu

ABSTRACT
A new two-parameter probability distribution called hypertabastic is introduced to model the survival or time-to-event data. A simulation study was carried out to evaluate the performance of the hypertabastic distribution in comparison with popular distributions. We then demonstrate the application of the hypertabastic survival model by applying it to data from two motivating studies. The first one demonstrates the proportional hazards version of the model by applying it to a data set from multiple myeloma study. The second one demonstrates an accelerated failure time version of the model by applying it to data from a randomized study of glioma patients who underwent radiotherapy treatment with and without radiosensitizer misonidazole. Based on the results from the simulation study and two applications, the proposed model shows to be a flexible and promising alternative to practitioners in this field.

Show MeSH
Related in: MedlinePlus