HYSTERECTOMY AND SUBSEQUENT RISK OF CANCER

Background. The objective of this retrospective cohort study was to as sess the effect of hysterectomy on subsequent risk of cancer among 25 382 hysterectomized and a similar number of non-hysterectomized contro l women, registered in 1963-1976 in the Mass Screening Registry (MSR). Methods. Cancer cases were obtained from the Finnish Cancer Registry (FCR) and standardized incidence ratio (SIR); the expected number of c ases based on cancer incidence rates of the Finnish female population in 1967-1993, was used. Relative risk (RR) was calculated as SIR among the hysterectomized relative to non-hysterectomized women, adjusted f or follow-up, education and parity. Results. The RR estimates of non-g enital cancers among women with any hysterectomy were approximately 5% higher than in the non-hysterectomized cohort. Relative risks of rect al cancer (RR = 1.4, 95% confidence interval [CI] : 1.0-1.8) and thyro id cancer (RR = 2.1, 95% CI:1.5-3.1) were significant and largest amon g women who had undergone total hysterectomy pre- or perimenopausally. Relative risk estimates of breast cancer were close to unity, Conclus ions. Hysterectomy is not associated with any substantial protective o r promoting effect on cancers in general. Elevated risk of papillary t hyroid cancer following hysterectomy is biologically plausible, as the re are reproductive and endocrinological causes of thyroid cancer.