the estimation of survival function for colon cancer data in tehran using non-parametric bayesian model

background: colon cancer is the third cause of cancer deaths. although colon cancer survival time has increased in recent years, the mortality rate is still high. the cox model is the most common regression model often used in medical research in survival analysis, but most of the time the effect of at least one of the independent factors changes over time, so the model cannot be used. in the current study, the survival function for colon cancer patients in tehran is estimated using non-parametric bayesian model. methods: in this survival study, 580 patients with colon cancer who were recorded in the cancer research center of shahid beheshti university of medical sciences since april 2005 to november 2006 were studied and followed up for a period of 5 years. survival function was plotted with non-parametric bayesian model and was compared with the kaplan–meier curve. results: of the total of 580 patients , 69.9 % of patients were alive. 45.9 % of patients were male and the mean age of cancer diagnosis was 65.12 (sd= 12.26) and 87.7 of the patients underwent surgery . there was a significant relationship between age at diagnosis and sex and the survival time while there was a non-significant relationship between the type of treatment and the survival time. the survival functions corresponding to the two treatment groups cross, in comparison with the patients who had no surgery in the first 30 months, showed a higher level of risk in the patients who underwent a surgery. after that, the survival probability for the patients undergoing a surgery has increased. conclusion: the study showed that survival rate has been higher in women and in the patients who were below 60 years at the time of diagnosis. please cite this article as : abadi a, ahmadi f, alavi majd h, akbari me, abolfazli khonbi z, davoudi monfared e. the estimation of survival function for colon cancer data in tehran using non-parametric bayesian model. iran j cancer prev. 2013; 6(3):141-6. references 1.     mathers cd, boschi-pinto c, lopez ad, murray cj. cancer incidence, mortality and survival by site for 14 regions of the world. geneva: world health organization. 2001;8. 2.     world health organisation. cancer. [cited 2009 april 21]. available from: http://www.who.int/cancer/en/ . 3.     sajadi a, nouraie m, mohagheghi m, mousavi-jarrahi a, malekezadeh r, parkin d. cancer occurrence in iran in 2002, an international perspective. asian pacific journal of cancer prevention. 2005;6(3):359. 4.     moghimi-dehkordi b, safaee a. an overview of colorectal cancer survival rates and prognosis in asia. world journal of gastrointestinal oncology. 2012;4(4):71. 5.     safaee a, moghimi-dehkordi b, fatemi s, ghiasi s, nemati-malek f, zali m. characteristics of colorectal mucinous adenocarcinoma in iran. asian pac j cancer prev. 2010;11:1373-5. 6.     fatemi sr, shivarani s, malek fn, vahedi m, maserat e, iranpour y, et al. colonoscopy screening results in at risk iranian population. asian pac j cancer prev. 2010;11:1801-4. 7.     cox dr. regression models and life-tables. journal of the royal statistical society series b (methodological). 1972:187-220. 8.     therneau tm, grambsch pm. modeling survival data: extending the cox model. new york: springer-verlag; 2000. 9.     de iorio m, johnson wo, müller p, rosner gl. bayesian nonparametric nonproportional hazards survival modeling. biometrics. 2009;65(3):762-71. 10.   lo ay. on a class of bayesian nonparametric estimates: i. density estimates. the annals of statistics. 1984;12(1):351-7. 11.   tokdar st. posterior consistency of dirichlet location-scale mixture of normals in density estimation and regression. sankhyā: the indian journal of statistics. 2006:90-110. 12.   ferguson ts. a bayesian analysis of some nonparametric problems. the annals of statistics. 1973:209-30. 13.   ferguson ts. prior distributions on spaces of probability measures. the annals of statistics. 1974:615-29. 14.   de iorio m, müller p, rosner gl, maceachern sn. an anova model for dependent random measures. journal of the american statistical association. 2004;99(465):205-15. 15.   escobar md. estimating normal means with a dirichlet process prior. journal of the american statistical association. 1994;89(425):268-77. 16.   west m. hyperparameter estimation in dirichlet process mixture models. discussion paper: duke university isds, usa; 1992. 17.   de carvalho vi, jara a, hanson te, de carvalho m. bayesian nonparametric roc regression modeling. bayesian analysis. 2013;1(1):1-21. 18.   mehrkhani f, nasiri s, donboli k, meysamie a, hedayat a. prognostic factors in survival of colorectal cancer patients after surgery. colorectal disease. 2009;11(2):157-61. 19.   rosenberg r, friederichs j, schuster t, gertler r, maak m, becker k, et al. prognosis of patients with colorectal cancer is associated with lymph node ratio: a single-center analysis of 3026 patients over a 25-year time period. annals of surgery. 2008;248(6):968-78. 20.   moradi a, khayamzadeh m, guya mm, mirzaei hr, salmanian r, rakhsha a, et al. survival of colorectal cancer in iran. asian pac j cancer prev. 2009;10:583-6. 21.   sudsawat laohavinij m, maneechavakajorn j. prognostic factors for survival in colorectal cancer patients. j med assoc thai. 2010;93(10):1156-66. 22.   fang h, wang x, feng f, wang j. [prognostic analysis of patients with liver metastases from colorectal cancer treated with different modes of therapy]. zhonghua zhong liu za zhi [chinese journal of oncology]. 2010;32(1):67-70. 23.   gharbi o, chabchoub i, limam s, hochlef m, ben fatma l, landolsi a, et al. [prognostic factors and survival of metastatic colorectal cancer in the sousse university hospital (tunisia): comparative study of two treatment period of 200 patients]. bulletin du cancer. 2010;97(4):445. 24.   moghimi-dehkordi b, safaee a, zali mr. prognostic factors in 1,138 iranian colorectal cancer patients. international journal of colorectal disease. 2008;23(7):683-8. 25.   zhang s, gao f, luo j, yang j. prognostic factors in survival of colorectal cancer patients with synchronous liver metastasis. colorectal disease. 2010;12(8):754-61. 26.   wang z, zhou z, liang j, bai x, bi j. [prognostic factors of colorectal cancer patients with synchronous liver metastasis treated with simultaneous liver and colorectal resection]. zhonghua zhong liu za zhi [chinese journal of oncology]. 2008;30(5):372-5. 27.   ghazali ak, musa ki, naing nn, mahmood z. prognostic factors in patients with colorectal cancer at hospital universiti sains malaysia. asian journal of surgery. 2010;33(3):127-33. 28.   nan k-j, qin h-x, yang g. prognostic factors in 165 elderly colorectal cancer patients. world journal of gastroenterology. 2003;9(10):2207-10. 29.   wardle j, mccaffery k, nadel m, atkin w. socioeconomic differences in cancer screening participation: comparing cognitive and psychosocial explanations. social science & medicine. 2004;59(2):249-61. 30.   groome p, schulze k, keller s, mackillop w. demographic differences between cancer survivors and those who die quickly of their disease. clinical oncology. 2008;20(8):647-56. 31.        vinnakota s, lam n. socioeconomic inequality of cancer mortality in the united states: a spatial data mining approach. international journal of health geographics. 2006;5(1):9.