Tubal sterilization and risk of ovarian, endometrial and cervical cancer. A Danish population-based follow-up study of more than 65 000 sterilized women

BACKGROUND: On the basis of a population-based cohort, we assessed the cancer risk, focusing on gynaecological cancers and pre-malignant lesions, among women with a previous tubal sterilization.

METHODS: Using the Danish Hospital Discharge Register we identified 65 232 women who had a tubal sterilization (1977-1993). The cohort was followed for cancer occurrence, and compared with the expected number based on the national cancer incidence rates.

RESULTS: The overall risk of ovarian cancer was decreased (standardized incidence ratio [SIR] = 0.82; 95% CI: 0.6, 1.0), and it was still decreased > or =10 years after the sterilization (SIR = 0.65; 95% CI: 0.4, 1.0). The rate of endometrial cancer was also decreased (SIR = 0.66; 95% CI: 0.5, 1.0), the risk continued being moderately reduced during follow-up, although it was not statistically significant.

CONCLUSIONS: In this nationwide, population-based study we find that women with tubal sterilization have a decreased risk of subsequent development of ovarian cancer. As the protective effect is not decreasing with years of follow-up, our data do not support that 'screening' bias can explain the protective effect, but indicate that the sterilization itself may convey a reduction in risk. The same pattern is found for endometrial cancer, the association being less strong.