Women who have had their ovaries removed may be at increased risk of colorectal cancer as a result of alteration in sex hormone levels, according to a population analysis in British Journal of Surgery.
Researchers assessed data from women who had undergone oophorectomy between 1965 and 2011, identified through the Swedish Patient Registry. Standard incidence rations (SIRs) and 95% confidence intervals (CIs) were calculated and then compared to the general population. Stratification was used for unilateral and bilateral oophorectomy as well as hysterectomy without specification of whether the ovaries had been removed.
During the study period, 195,973 women underwent oophorectomy and 3150 women (1.6%) were subsequently diagnosed with colorectal cancer (median follow-up: 18 years). Among the oophorectomized women, risk of colorectal cancer was increased compared with the general population (SIR: 1.30. 95% CI 1.26-1.35). Risk was lower in women who were younger at the age of oophorectomy (15–39 years: SIR: 1.10, 95% CI 0.97 to 1.23; 40–49 years: SIR 1.26, 95% CI 1.19 to 1.33; P for trend < 0.001). The highest risk period was 1 to 4 years following oophorectomy (SIR: 1.66, 95% CI 1.51 to 1.81; P<0.001).
Following multivariate analysis, women who underwent a bilateral oophorectomy seemed to have a higher risk of colorectal cancer than women who had a unilateral procedure (hazard ratio 2.28, 95% CI 1.33 to 3.91).
The researchers concluded that there appeared to be an increased risk of colorectal cancer following oophorectomy which was performed for benign indications.