Page 63 - ISMCON souvenir 2021

ISMSCON - 2021

to refrain from availing scientific mental health service and treatment modes. There are observable
differences in using of tertiary mental health services among people of different castes, gender and
socio-economic backgrounds.
Aim: To see the differences in mental health services utilization across caste and gender.
Method: This study is retrospective in nature. This study is based on a retrospective analysis of routinely
recorded patients’ related clinical data collected during 2012 and 2017.
Conclusion: In the present study, it was noted that, within the span of 05 years, there is more than
19.68% increase in patients’ registration at OPD level. In the present study, it was noted that, in case of
new as well as follow-up cases males have always constituted an overwhelming majority than females. In
the context of new cases (patients coming to the Institute for the first time), the number of male patients
almost doubled during 2012 to 2017 and at the time of follow-up, this difference was seen to further
increase to nearly 2½ times.
Keywords: Mental Health, Gender difference, Services utilization.

OS27: Cancer Survival Risk Estimationusing Gamma Frailty
Model

K M Jagathnath Krishna , T Traison , Sejil Mariya Sebastian , Preethi Sara George ,
1
1
2
1
Aleyamma Mathew 1
1Division of Cancer Epidemiology & Biostatistics, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
2Department of Statistics, Pondicherry University, Pondicherry, India
E-mail:jagath.krishna@gmail.com

Abstract:

Background: In time to event analysis, the risk for an event is usually estimated using Cox proportional
hazards (CPH) model. But CPH model has the limitation of biased estimate due to unobserved hidden
heterogeneity among the covariates, which can be tackled using frailty models. The best models were
usually being identified using Akaike information criteria (AIC). Apart from AIC, the present study aimed
to assess predictability of risk models using survival concordance measure.
Methods: CPH model and frailty models were used to estimate the risk for breast cancer patient survival,
and the frailty variable was assumed to follow gamma distribution.Schoenfeld global test was used to
check the proportionality assumption. Survival concordance, AIC and simulation studies were used to
identify the significance of frailty.
Result:From the univariate analysis it was observed that for the covariate age,the frailty has a significant
role (θ=2.758, p-value: 0.0004) and the corresponding hazard rate was 1.93 compared to that of 1.38
for CPH model (Age > 50 v/s ≤ 40). Also the covariates radiotherapy and chemotherapy were found to
be significant (θ=5.944, p-value: <0.001 and θ= 16, p-value: <0.001 respectively). Even though there
were only minor differences in hazard rates, the concordance was higher for frailty than CPH model for
all the covariates. Further the simulation study showed that the bias and root mean square error (RMSE)
obtained for both the methods was almost the same and the concordance measures were higher for
frailty model by 12% to 15%.

Conclusion: We conclude that the frailty model is better compared to CPH model as it can account for
unobserved random heterogeneity, and if the frailty coefficient doesn’t have an effect it gives exactly the
same risk as that of CPH model and this has been established using survival concordance.
Keywords: Cox Proportional Hazards, Frailty, Concordance measure, Simulation, Breast Cancer

CONFERENCE SOUVENIR 61