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International Journal of Cancer Research
  Year: 2006 | Volume: 2 | Issue: 1 | Page No.: 10-18
DOI: 10.3923/ijcr.2006.10.18
 
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Disease-free Survival and Metastases Pattern in Breast Cancer Patients after Mastectomy: An Application of Stratified Markov Model

M.R. Gohari , M. Mahmoudi , K. Mohammed , Y. Pasha and R. Khodabakhshi

Abstract:
This study designed and carried out to determine the disease-free survival of breast cancer patients after surgery and to assess its associated factors. The variability in effect of prognostic factors over time was also assessed. For this purpose one hundred seventeen women with breast cancer operated on at three hospitals in Tehran, Iran between 1990 and 2003 were enrolled in study. Since the occurrences of successive metastases in any patient are correlated and the occurrence of one metastasis may make further events more or less likely we used a Stratified Markov model to account for within-subject correlation in event times. This model stratifies data by event so that the baseline hazard is allowed to vary with each metastasis. In this model effect of covariates on the hazard of event is also estimated in each stratum, separately. The variables of age at time of surgery, number of positive lymph nodes, histologic grade, size of tumor, ER status, P53 and Her2 were considered in the model. Median follow up time for patients in study was 26 months after surgery. During the follow up time 44(38%) patients developed metastasis. 20(45%) of those experienced the second metastasis. The median disease-free survival for patients in study was 49.6 month and the median time to experience the second metastasis was 22.5 month. Risk of occurrence of a metastasis in the first year after mastectomy was 12%. Up to the second and fifth years risk of experience a metastasis was 32 and 69%, respectively. The rate of metastasis in our study was higher than some other countries. One reason for highly rate of relapse in patients is the fact that patients sought medical attention when the disease has reached an advanced stage. Stratified Markov model showed that the effect of prognostic factors was different for the first and the second metastasis. Size of tumor and number of positive lymph nodes had a significant effect on the risk of first metastasis. While tumor size was the only factor that affected hazard of the second metastasis. One possible reason for this finding is that the effect of these factors was mixed with the effect of time to first metastasis and we can`t separate them in analysis of the second time.
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How to cite this article:

M.R. Gohari , M. Mahmoudi , K. Mohammed , Y. Pasha and R. Khodabakhshi , 2006. Disease-free Survival and Metastases Pattern in Breast Cancer Patients after Mastectomy: An Application of Stratified Markov Model. International Journal of Cancer Research, 2: 10-18.

DOI: 10.3923/ijcr.2006.10.18

URL: https://scialert.net/abstract/?doi=ijcr.2006.10.18

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