Influence of prior and subsequent pregnancy on breast cancer prognosis.

PURPOSE AND METHODS: The prognostic influence of pregnancies 5 years before (n = 173) and after (n = 50) breast cancer diagnosis was investigated in 2,119 women less than 50 years of age with a primary operable breast cancer. The main end point was distant metastasis. Univariate and multivariate analyses were performed using the Cox proportional hazards model. In the analyses of the effect of pregnancy after diagnosis of breast cancer, a Cox model with a time-dependent covariate was applied. RESULTS: Women with a pregnancy before diagnosis had slightly larger tumors than the control group. However, they did not differ with respect to nodal status and estrogen receptor (ER) status. There was no evidence that women with a pregnancy during the 5-year period preceding breast cancer diagnosis had a worse prognosis compared with women without pregnancy during the same period. Similarly, there was no evidence that women with a pregnancy after breast cancer diagnosis had a worse prognosis. CONCLUSION: The hormonal changes associated with pregnancy thus seem to have little, if any, influence on the prognosis of breast cancer. In the present study, at least, there was no indication of a worse prognosis. In fact, the relative hazard for women who became pregnant after diagnosis of breast cancer in comparison with women without a subsequent pregnancy was 0.48 (P = .14), which suggested a possible decreased risk of distant dissemination.