Incidence of ovarian cancer after hysterectomy: a nationwide controlled follow up.

OBJECTIVE

To estimate the risk of developing ovarian cancer after abdominal (total or subtotal) hysterectomy on benign indication.

DESIGN

Prospective historical cohort study with 12.5 years of follow up.

SETTING

Denmark, nationwide.

POPULATION

All Danish women (aged 0 to 99 years) having undergone hysterectomy with conservation of at least one ovary for a benign indication from 1977 to 1981 (n = 22,135). Follow up was conducted from 1977 to 1991. The reference group included all Danish women who had not undergone hysterectomy, age-standardised according to the hysterectomy group (n = 2,554,872).

METHODS

Registry data derived from the Danish National Register of Patients (diagnoses and operation codes) and the Civil Registration System (information about general population, including time of death).

MAIN OUTCOME MEASURES

Incidence rate of ovarian cancer, lifetime risk of ovarian cancer, relative risk of ovarian cancer.

RESULTS

Seventy-one women developed ovarian cancer on average 7.0 years after hysterectomy and 10,659 women in the reference group had ovarian cancer diagnosed after on average 6.4 years. The incidence rate of ovarian cancer was 0.27 per 1000 person-years in the group that had undergone hysterectomy and 0.34 per 1000 person-years in the general population (age-standardised). The extrapolated lifetime risk of developing ovarian cancer was 2.1% after hysterectomy and 2.7% in the general population (RR 0.78; 95% CI 0.60-0.96).

CONCLUSIONS

The risk of ovarian cancer is lower among women who have undergone hysterectomy compared with those who have not. The protection seems to decrease with time.