Iranian Journal of

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Background & Objectives: Identifying the important influential factors is a great challenge in oncology studies. Decision tree is one of methods that could be used to evaluate the prognostic factors and classifying the patients' homogeneously. This method identifies the main prognostic factors and then determines the subgroups of patients based on those prognostic factors. The aim of this study was to assess the prognostic factors and homogeneous subgroups of colorectal patient through survival tree.
Methods: Data collected from an observational of 739 colorectal patients registered in the cancer registry affiliated to the center of Research Center of Gastroenterology and Liver Disease (RCGLD), Shahid Beheshti Medical University, Tehran, Iran. Death was the interested event and the survival time was calculated from date of diagnosis until occurrence of event (or censoring) in months. Finally we used decision tree based method for classifying and analyzing the data.
Results: Based on our result, decision tree identified four covariates as important prognostic factors in 0.05 significant levels: general stage of cancer, age of diagnosis, histology of tumor and morphology type of tumor. Also patients based on these prognostic factors divided into five homogeneous subgroups. The greater values of measure of separation (SEP) criterion support the appropriateness of this model for such the data.
Conclusion: Decision tree is powerful and intuitive method. It has a key feature that is in addition to evaluate the prognostic factors, provides the homogeneous subgroups for future analysis.

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  Background and Objectives : The aim of this study was to assess the disease trajectory and recurrence rate of pemphigus based on the analysis of the gap time between successive recurrent events. In this regard, the most important associated factors with the risk of recurrence could be explained.

  Methods: This longitudinal study was performed on 112 pemphigus patients who attended the dermatology department of Imam Khomeini Hospital, Tehran, Iran, from March 2006 to January 2013. The study duration was considered from the diagnosis of the disease to December 2013. Recurrent events were analyzed based on the gap time between successive events using the multivariate time dependent frailty model. The time between two recurrent gap times was determined monthly between two successive events.

  Results : Decreasing the gap times between two successive events indicates that the subsequent event after the first recurrence occurs with shorter time intervals. So, the disease trajectory represents an increase in the recurrence rate over time. Based on the results of multivariate frailty model, IgG antibody's level was the only effective factor on the recurrence hazard rate of the patients. Also, this model proved that the frailty effects were time dependent frailties.

  Conclusion: Assessing the disease trajectory and recurrence hazard rate can be achieved through analyzing the gap time between successive recurrent events. This analysis also identifies the factors that influence the risk of subsequent recurrent events.

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Background and Objectives: Breast cancer is the leading cause of death from cancer among women. In developing countries, the patients’ survival is less than developed countries. Metastasis, as an intermediate event, affects the survival of breast cancer patients. This study aimed to evaluate the survival of patients after surgery considering metastasis, as the intermediate event, using the illness-death model.
Methods: In this study, 165 cases of Iranian breast cancer patients who underwent surgery during 2006-2014 were investigated. The patients’ characteristics and their intermediate and final status were collected from their medical records. The illness-death model was used to assess prognostic factors in all stages of disease.
Results: The risk of metastasis in patients with tumor size between 2-5 cm was 3.8 times higher than patients whose tumors were below 2 cm (P=0.009). Patients who had 3 to 6 lymph nodes involved were 3.1 times more likely to have metastases that those with less than 2 lymph nodes (P=0.003). Also, the grade of tumor and HER-2 had a significant role in metastasis (P=0.04).
Conclusion: Using the illness-death model that is suitable for the analysis of such data, it was found that lymph node involved and tumor size had a significant role in metastasis. So, early detection of cancer is required to prevent metastasis and death.