To determine the effect of estrogen replacement therapy (ERT) on recurrence rate and survival in women who have undergone surgery for stage I or II endometrial cancer.

After surgery, eligible patients were allocated to therapy with ERT or placebo after undergoing hysterectomy with or without pelvic and aortic nodal sampling. Planned duration of hormonal versus placebo treatment was 3 years, with an additional 2 years of follow-up.

The median follow-up time for all 1,236 eligible and assessable patients was 35.7 months. Stage, grade, histologic subtype, and percentage of patients receiving adjuvant therapy were similarly distributed between the groups. The median age at diagnosis for the 618 patients randomly assigned to ERT was 57 years (range, 26 to 91 years). Two hundred fifty-one patients (41.1%) were compliant with ERT for the entire treatment period. Disease recurrence was experienced in 14 patients (2.3%). Eight patients (1.3%) developed a new malignancy. There were 26 deaths (4.2%), and five deaths (0.8%) were a result of endometrial cancer. The median age at diagnosis for the 618 patients in the placebo group was 57 years (range, 30 to 88 years). Twelve patients (1.9%) experienced disease recurrence. Ten patients (1.6%) developed a new malignancy. There were 9 deaths (3.1%) in the placebo group, and four deaths (0.6%) were a result of endometrial cancer.

Although this incomplete study cannot conclusively refute or support the safety of exogenous estrogen with regard to risk of endometrial recurrence, it is noteworthy that the absolute recurrence rate (2.1%) and the incidence of new malignancy were low.