Description
Reproductive and hormonal factors have long been associated with the risk of primary breast cancer, but the associations with prognosis and recurrence are less clear. Currently, oncologists use disease characteristics, a woman's age, and family history in order to determine a course of treatment for an early-stage breast cancer patient. The purpose of this cohort study was to clarify possible relationships between reproductive history, and its underlying hormonal mechanisms, with breast cancer prognosis and recurrence. Study participants (n = 2336) were early stage breast cancer patients (stage I-IIIA) diagnosed within the previous four years. They were categorized into three breast cancer outcome groups: no evidence of recurrence event, locoregional recurrence/new primary tumor, and distant recurrence/metastasis, and the risk of both types of recurrence were compared to the recurrence-free group on several tumor characteristics, treatments received, and reproductive history. The effects of parity were examined through analysis of recurrence-free interval and overall survival based on parity categories using Cox Proportional Hazards modeling and the Kaplan-Meier method. Without adjusting for other variables, women who had two or more live births (the median number of live births in the sample) had significantly better disease-free intervals than women with zero or one full-term pregnancy. In terms of overall survival, women with 1-2 live births (between 25th and 75th percentiles) had the best survival, women with 3+ (above the 75th percentile) live births had intermediate survival, and nulliparous women (below the 25th percentile) had the worst survival. After adjusting for other predictors, the hazard ratio for parity was significant at the 0.1 level for locoregional recurrence as well as recurrence of any type, and the relationship changed over time for each additional live birth. The reproductive history variables age at menarche and age at menopause had significant associations with risk of distant metastasis.
