Women with surgically diagnosed endometriosis: Incidence, risk of cancer and death

The aim of this thesis was to assess the risk of cancer according to the types of endometriosis and the risk of death among women with surgically verified endometriosis.\n\nIn first register-based cohort study, all women with an initial endometriosis diagnosis (49 956 women) undergoing a relevant surgical procedure were identified from the Finnish Hospital Discharge Register from 1987 to 2012. The cohort was divided into sub-cohorts of ovarian (n=23 222), peritoneal (n=20 197), and deep infiltrating endometriosis (n=2372) according to the procedural diagnosis. Between 1987 and 2012 the median age at index surgery decreased 38.8-34.0 years (interquartile range 32.3–43.6; 28.9–41.0) and the age-standardized incidence rate decreased from 116-45 (95% confidence interval [CI] 112–120; 43-48) per 100 000 women.\n\nIn second and third study, all female cancer cases were identified from the Finnish Cancer Registry until the end of 2014 (840 000 person-years). The overall risk of cancer mirrored that of the Finnish general female population (standardized incidence ratio 0.98; 95%CI 0.95–1.01). Of all gynecological cancers, the risk of\novarian cancer increased (1.76; 1.47–2.08). It was highest among women with ovarian endometriosis and especially for endometrioid and clear-cell ovarian cancer. In contrast, the incidence of precancerous lesions of the uterine cervix (0.81; 0.71–0.92) and that of invasive squamous cell cervical cancer (0.46; 0.20–0.91) decreased. Of all non-gynecological cancers, the risk of thyroid cancer (1.43; 1.23–1.64) and that of basal cell carcinoma increased (1.18; 1.10–1.25). In comparison, the risk of mouth and pharynx cancers (0.60; 0.41–0.80) and of pancreatic cancer (0.76; 0.58–0.96) decreased.\n\nIn fourth study, the data on the deaths was obtained from Statistics Finland until the end of 2014. The reference cohort (n=98 824) included two age- and municipality-matched women for each woman in the endometriosis cohort. The risk of death from any cause decreased (adjusted mortality rate ratio [MRR] 0.73; 0.69–0.77) in the endometriosis cohort. Furthermore, the adjusted MRR difference remained significant during 24 years of follow-up. Mortality was lower due to cardiovascular diseases (0.57; 0.50–0.65), including ischemic heart and cerebrovascular diseases, as well as due to accidents and violence, diseases of the respiratory and digestive systems, alcohol-related causes, and other causes.\n\nIn conclusion, only a few types of cancer carry an increased or decreased risk with mid-life women among\nsurgically diagnosed endometriosis. Ovarian endometriosis was most strongly associated with increased risk\nof ovarian cancer. The overall mortality and cardiovascular mortality were decreased among these women.