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A Bayesian joint model for multivariate longitudinal and time-to-event data with application to ALL maintenance
Damitri Kundu1, Partha Sarkar2, Manash Pratim Gogoi3
1Applied Statistics Division, Indian Statistical Institute, Kolkata, India.
Insights
This study on childhood Acute Lymphocytic Leukemia (ALL) found that neutrophil and platelet counts, not white blood cell counts, predict relapse. Lower 6MP and higher MTx doses reduced relapse probability in ALL patients.
Area of Science:
- Pediatric Oncology
- Biostatistics
- Translational Cancer Research
Background:
- Acute Lymphocytic Leukemia (ALL) is the most common childhood cancer.
- Standard treatments involve drugs like 6-mercaptopurine (6MP) and methotrexate (MTx).
- Identifying biomarkers for relapse prediction and treatment effectiveness is crucial.
Purpose of the Study:
- To identify longitudinal biomarkers associated with time-to-relapse in pediatric ALL patients.
- To assess the effectiveness of 6MP and MTx treatments in relation to relapse.
- To develop and validate a statistical model for analyzing longitudinal biomarkers and time-to-relapse.
Main Methods:
- A Bayesian joint model was developed, integrating a linear mixed model for longitudinal biomarkers (white blood cell, neutrophil, platelet counts) and a semi-parametric proportional hazards model for time-to-relapse.
- The model analyzed data from 236 pediatric ALL patients treated at TTCRC, Kolkata.
- The model's ability to assess covariate effects and impute missing data was evaluated.
Main Results:
- Neutrophil and platelet counts were significantly associated with time-to-relapse in ALL patients.
- White blood cell count showed no significant association with time-to-relapse.
- Lower 6MP doses and higher MTx doses were linked to a reduced probability of relapse.
- Patients classified as "high-risk" at presentation exhibited the lowest relapse probability.
Conclusions:
- The developed Bayesian joint model effectively identifies biomarkers predicting relapse in pediatric ALL.
- Neutrophil and platelet counts are critical prognostic indicators for ALL relapse.
- Treatment strategies involving adjusted 6MP and MTx dosages may influence relapse rates, with potential implications for high-risk groups.
Abstract:
The most common type of cancer diagnosed among children is the Acute Lymphocytic Leukemia (ALL). A study was conducted by Tata Translational Cancer Research Center (TTCRC) Kolkata, in which 236 children (diagnosed as ALL patients) were treated for the first two years (approximately) with two standard drugs (6MP and MTx) and were then followed nearly for the next 3 years. The goal is to identify the longitudinal biomarkers that are associated with time-to-relapse, and also to assess the effectiveness of the drugs. We develop a Bayesian joint model in which a linear mixed model is used to jointly model three biomarkers (i.e. white blood cell count, neutrophil count, and platelet count) and a semi-parametric proportional hazards model is used to model the time-to-relapse. Our proposed joint model can assess the effects of different covariates on the progression of the biomarkers, and the effects of the biomarkers (and the covariates) on time-to-relapse. In addition, the proposed joint model can impute the missing longitudinal biomarkers efficiently. Our analysis shows that the white blood cell (WBC) count is not associated with time-to-relapse, but the neutrophil count and the platelet count are significantly associated with it. We also infer that a lower dose of 6MP and a higher dose of MTx jointly result in a lower relapse probability in the follow-up period. Interestingly, we find that relapse probability is the lowest for the patients classified into the "high-risk" group at presentation. The effectiveness of the proposed joint model is assessed through the extensive simulation studies.
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