AbstractsMedical & Health Science

Both ovarian and tubal cancers are rare. Therefore only a few studies explored such postmenopausal hormone therapies (HT) as used in Finland, as a risk factor for these cancers. I compared the incidence of ovarian and tubal cancer in HT users with the incidences of these cancers in the background population in two nationwide cohort studies. To exclude a number of potential confounders I conducted two case-control studies to further elucidate HT use as a risk factor for these cancers. The cohort studies included all women aged 50 or older who had used HT-regimens for 6 months or longer in 1994-2008. These women were identified from the Finnish Medical Reimbursement Register. The ovarian cancer cohort study included 224,015 women using estradiol-progestin therapy (EPT), whereas in the primary fallopian tube carcinoma (PFTC) cohort study included altogether 365,601 women using EPT (n=247,781) or estradiol-only therapy (ET)(n=117,820). These women were followed from the first HT purchase to the diagnosis of ovarian or tubal cancer, death, emigration or to the end of the study period through the national Finnish Cancer Registry. Relative risks of these cancers in HT users were estimated by comparing the incidence of ovarian or tubal cancer in HT users to the age-matched comparable background population and calculating standardized incidence ratios (SIR) and their 95% confidence intervals (CI). In the case-control studies, all 50-year-old or older women with incident ovarian cancer (n=3,958) or PFTC (n= 360) during 1995-2007 were identified from the Cancer Registry. The Population Register provided control women, 3 per each case of ovarian cancer and 10 per each case of PFTC, and parity data. The controls had to be alive and without ovarian/primary fallopian tube cancer and they were matched for age (+/- one month) and place or residence. The controls with an oophorectomy (n=506) or a salpingectomy (n=158) were excluded leaving 11,325 and 3,442 controls, respectively. Odds ratios (OR) with 95% CIs for various HT regimens were estimated by using conditional logistic regression adjusted for parity, ages at deliveries, hysterectomy and sterilization. The use of any type of EPT for less than five years did not modify the overall risk of ovarian cancer. Instead, the use of sequential EPT for five years or longer was associated with an elevation in the overall risk of ovarian cancer (SIR 1.21, 95% CI 1.06-1.37). The risk rises were most marked for serous (1.56; 1.33-1.80) and mixed cancer (1.54; 1.22-1.91) whereas the risk for mucinous cancer was decreased (0.47; 0.22-0.86). The risk increase connected to EPT use did not depend on the progestin type, mode or route of administration of EPT. The use of ET for five years or longer was linked with an increase in the risk for serous ovarian cancer (OR 1.45, 95% CI 1.20-1.75) while the risk of mucinous cancer was decreased (0.35; 0.19-0.67). As a whole the use of ET was accompanied with borderline rise in overall ovarian cancer risk (1.15; 0.99-1.32). In the users of…