A cohort study of topical vaginal estrogen therapy in women previously treated for breast cancer

To estimate the risk of recurrence of breast cancer associated with the use of topical vaginal estrogen therapy in the management of vaginal atrophy in women previously treated for breast cancer. The study group comprised 1472 women with histologically confirmed breast cancer. In 69 of these subjects (4.7%) their only bothersome menopausal problems were vaginal symptoms. In these women, poorly absorbed topical vaginal estrogen cream or tablets were used. The response of these patients was compared with that of the rest of the database. A Cox regression analysis was performed using sex hormone usage after diagnosis as a time-dependent covariate. Disease-free interval was the outcome measured. Results are expressed as a hazard ratio with 95% confidence intervals. The hazard rate is defined as the probability of disease recurrence or of a subject dying from breast cancer over the study period. A second analysis was performed adjusting for factors known to affect breast cancer prognosis. Hormone usage was entered as a time-dependent covariate with disease-free interval as the outcome. Subjects who used a topical estrogen alone for menopausal symptoms had an uncorrected hazard ratio of 0.30 (95% confidence interval (CI) 0.11-0.80, p = 0.02). The corrected hazard ratio was 0.57 (95% CI 0.20-1.58, p = 0.28). The hazard rate for a subject dying was not analyzed, as there were too few numbers. Although the small numbers of this study preclude a definitive result, topical estrogen usage does not appear to be associated with an increased risk of recurrence of breast cancer.