The influence of exogenous estrogen use on survival after diagnosis of endometrial cancer.

For examination of the effect of prior exogenous estrogen use on survival after diagnosis of endometrial cancer, 244 endometrial cancer cases newly diagnosed at North Carolina Memorial Hospital, Chapel Hill, North Carolina, between 1970 and 1976 were followed until 1982. Estrogen users (n = 46) were younger, had less advanced disease, and were more likely to be nonobese and white than were nonusers (n = 198). The estimated probability of surviving (Kaplan-Meier) five years after diagnosis was 0.89 for users and 0.53 for nonusers. When adjusted for age, grade, stage, obesity, race, and treatment (using the Cox proportional hazards regression model), the survival probabilities throughout the period of observation for estrogen users continued to be higher. The adjusted hazard rate for a nonuser was 2.05 (95% confidence interval (Cl) 0.96-4.39) times that for an estrogen user. The adjusted hazard rate from endometrial cancer only was 4.01 (95% Cl 1.22-13.21) times greater among estrogen nonusers. The more frequent occurrence of endometrial cancer in an earlier stage and grade among estrogen users may not be the sole cause of their lower hazard rate from this disease.