“…Clinical indicators of prognosis that were entered as predictor variables into the Cox model were age (continuous), tumor size (continuous), lymph node involvement (yes, no, unknown), distant metastasis (yes, no), tumor grade (low, medium, high, unknown), estrogen receptor status (yes, no, unknown), and progesterone receptor status (yes, no, unknown). Ethnicity, which is a prognostic predictor of survival, was also included in the model [7]. Observation times of women were calculated as time between diagnosis and death (all causes), last contact or November 2010.…”