Prognostic significance of etiological risk factors in early breast cancer.

Several risk factors for the etiology of breast cancer have also been correlated with the prognosis of breast cancer. However, the published studies have yielded conflicting results. Women under 71 years of age with stage I, II, or III breast cancer were eligible for inclusion in a clinical study. 866 patients with breast cancer entered the study, of whom 463 had positive lymph nodes. Survival was analysed using Cox's proportional hazards model. Age at menarche parity, age at menopause and family history were not consistently related to survival. Young age at first full-term pregnancy was related to decreased survival (adjusted relative risk (RR): 1.69, 95% confidence intervals (95% CI): 1.04-2.68), but it cannot be excluded that this result was due to chance alone. Use of oral contraceptives was not correlated with survival (RR: 1.10, 95% CI: 0.80-1.51) nor was family history (RR: 0.93, 95% CI: 0.66-1.30). This study provided little support for the hypothesis that risk factors for breast cancer are related to survival.