Why is this important?
The association between hormonal treatment of menopause and the risk of breast or endometrial cancer is well established, however the risk vis-à-vis ovarian cancer is less clear. The strength of this study lies in the fact that it is prospective, conducted on a large cohort, with long follow-up and data crossing self-declarations and drug dispensing.
Methodology
This study included a population of postmenopausal women from the E3N study. Exposure to a THM was identified through self-administered questionnaires between 1992 and 2004 and from cohort-matched drug claims data between 2004 and 2014.
Principle results
A total of 75,606 women were included. Among them, 31% had never used THMs, 67% had already taken them and 2% did not know whether they had taken them or not. Of the women who had ever been exposed to a THM, 25% had taken estrogen alone, 61% estrogen and progesterone or dydrogesterone, and 61% estrogen and another progestogen.
During the mean follow-up of 15.3 years, 416 primary ovarian cancers were diagnosed.
In multivariate analyses, compared to women who had never taken HRT, the risk of ovarian cancer was not significant for those who had been exposed to estrogen alone (Hazard ratio adjusted for age or HRa 1, 09 [0,82-1,46]) compared to those that had never been exposed. On the other hand, it was increased in women exposed to an estrogen combined with progesterone or dydrogesterone (HRa 1.28 [1,04-1,57]) and decreased by 19% (HRa 0.81 [0,65-1,00], p=0.053; borderline significant) in women exposed to estrogen and another type of progestogen.
The associated risk of ovarian cancer decreased significantly with the time elapsed since the last use only for the estrogen + progesterone or dydrogesterone combination. No significant variation was observed according to the duration of use, the practice of a hysterectomy, the previous use of oral contraceptives or the BMI, and this whatever the THM treatment considered.
