Modeling of Breast Cancer Prognostic Factors Using a Parametric Log-Logistic Model in Fars Province, Southern Iran

In general, breast cancer is the most common malignancy among women in developed as well as somedeveloping countries, often being the second leading cause of cancer mortality after lung cancer. Using aparametric log-logistic model to consider the effects of prognostic factors, the present study focused on the5-year survival of women with the diagnosis of breast cancer in Southern Iran. A total of 1,148 women who werediagnosed with primary invasive breast cancer from January 2001 to January 2005 were included and dividedinto three prognosis groups: poor, medium, and good. The survival times as well as the hazard rates of the threedifferent groups were compared. The log-logistic model was employed as the best parametric model which couldexplain survival times. The hazard rates of the poor and the medium prognosis groups were respectively 13 and3 times greater than in the good prognosis group. Also, the difference between the overall survival rates of thepoor and the medium prognosis groups was highly significant in comparison to the good prognosis group. Use ofthe parametric log-logistic model - also a proportional odds model - allowed assessment of the natural processof the disease based on hazard and identification of trends.