CANCER RISK AFTER A HOSPITAL DISCHARGE DIAGNOSIS OF ENDOMETRIOSIS

OBJECTIVES: Our goal was to determine the risk of cancer after hospita lization for endometriosis. STUDY DESIGN: Records of 20,686 women hosp italized with endometriosis during the period 1969 to 1983, as identif ied through the nationwide Swedish Inpatient Register, were linked aga inst the National Swedish Cancer Registry through 1989 to identify all subsequent diagnoses of cancer. The study subjects were followed up f or a mean of 11.4 years, with the cohort contributing 216,851 woman ye ars of follow-up. Standardized incidence ratios were computed by the u se of age- and period-specific incidence rates derived from the Swedis h population. Because of the high proportion of subjects with gynecolo gic operations (55.6%), evaluation of the risk of gynecologic cancers involved truncation of person years at the time of any such operation. RESULTS: The overall cancer risk was 1.2 (95% confidence interval 1.1 to 1.3). Significant excesses were observed for breast cancer (standa rdized incidence ratio = 1.3, 95% confidence interval 1.1 to 1.4), ova rian cancer (1.9, 1.3 to 2.8), and hematopoietic malignancies (1.4, 1. 0 to 1.8); this latter excess was largely driven by an excess risk of non-Hodgkin's lymphoma (1.8, 1.2 to 2.6). The risk of ovarian cancer w as particularly elevated among subjects with a long-standing history o f ovarian endometriosis (4.2, 2.0 to 7.7). Cervical cancer risk was sl ightly reduced (0.7, 0.4 to 1.3) whereas no association was observed f or cancer of the endometrium (1.1, 0.6 to 1.9). CONCLUSIONS: These fin dings suggest that further attention be given to the risk of breast, o varian and hematopoietic cancers among women with endometriosis and to exploring possible hormonal and immunologic reasons for the excess ri sks.