Oophorectomy Increased Risk for Colorectal Cancer

Women who have undergone oophorectomy may be at an increased risk for colorectal cancer, according to the results of a study published in the British Journal of Surgery.

The study found that women who had their ovaries removed for benign reasons had a 30% increased incidence of colorectal cancer compared with the general population.

According to researcher J. Segelman, of Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden, and colleagues, the study “emphasizes that prophylactic resection of normal ovaries should be reserved for women with a clear indication.”

Prior research has shown that hormonal factors may have an influence on colorectal cancer risk. Specifically, women have a lower incidence and mortality from the disease compared with men, and women on hormone replacement therapy or oral contraceptives also have a reduced risk.

Therefore, in this population-based analysis, Segelman and colleagues examined if oophorectomy altered risk for colorectal cancer. The researchers looked at a group of almost 200,000 women from the Swedish Patient Registry who had undergone oophorectomy between 1965 and 2011. Of the total cohort, 3,150 women were later diagnosed with colorectal cancer.

Calculating a standard incidence ratio (SIR), the researchers found that having undergone oophorectomy was associated with an increased risk for colorectal cancer (SIR, 1.30; 95% CI, 1.26–1.35). Younger women aged 15 to 39 had a lower risk for colorectal cancer with an SIR of 1.10 (95% CI, 0.97–1.23) compared with an SIR of 1.26 for women aged 40 to 49 (95% CI, 1.51–1.81; P < .001).

“An explanation might be the potentially protective effect of exogenous estrogen on colorectal cancer risk, as estrogen substitution after oophorectomy was probably more common in younger than in older age groups,” the researchers wrote.

Women who had both ovaries removed had an increased incidence of colorectal cancer compared with women who had only one ovary removed (SIR 1.35 vs 1.20), but the difference was not statistically significant. Risk for colorectal cancer was highest shortly after the procedure. The SIR was 1.66 for years 1 to 4 post-procedure compared with an SIR of 1.15 for 5 to 9 years after the procedure and 1.28 for 10 or more years afterward (P < .001 for trend).

The researchers acknowledged that one limitation to the study was that other potential risk factors for colorectal cancer were not available.