Cancer Risk After Hospital Discharge Diagnosis of Benign Ovarian Cysts and Endometriosis

Abstract

Using the Swedish Hospital Discharge Register, the authors identified all Swedish women born before 1970 who had been hospitalized for benign ovarian cyst (n = 42,217), functional ovarian cyst (n = 17,998), or endometriosis (n = 28,163). To serve as controls, they matched each study patient to 3 women listed in the Swedish Population Register with the same birth date. The National Swedish Cancer Register was then used to identify any of these subjects or controls who developed gynecologic cancer. Women who had undergone ovarian cyst resection and/or unilateral oophorectomy had a much higher risk of ever developing ovarian cancer than those who had not (odds ratio [OR], 8.8; 95% confidence interval [CI], 0.35-0.66 vs. OR, 0.48; 95% CI, 5.5-14.8). Whether or not they underwent surgery, women who were hospitalized with a benign or function ovarian cyst when they were 10 to 29 years of age had an increased risk of ovarian cancer later in life (OR for benign cyst, 2.23; 95% CI, 1.29-3.86; OR for functional cyst, 1.76; 95% CI, 1.5-2.0). Women in this age group with endometriosis had an even higher risk of later ovarian cancer (OR, 3.52; 95% CI, 1.56-7.95). However, women who developed an ovarian cyst after the age of 50 years were at decreased risk for subsequent ovarian cancer. When all age groups were combined, there remained an association between endometriosis and later development of ovarian cancer (OR, 1.34; 95% CI, 1.03-1.75). Benign or functional ovarian cysts were not associated with ovarian cancer over all age groups. Nulliparity was a significant factor in the development of ovarian cancer among women who had functional ovarian cysts or endometriosis. The odds ratios for the development of ovarian cancer were 2.28 and 1.89, respectively (95% CI, 1.18-4.37 and 1.19-3.01), for nulliparous women. For women who had 4 or 5 pregnancies before being hospitalized for functional cyst or endometriosis, the odds ratios were 1.01 and 1.27 (95% CI, 0.19-5.29 and 0.24-6.63), respectively. Compared with the control group, women who were hospitalized for benign ovarian cyst developed ovarian cancer at a younger age (47.6 vs. 54.1 years; P <0.001). Similarly, women who were hospitalized for a functional ovarian cyst or endometriosis were diagnosed with ovarian cancer at a younger age than controls (40.7 vs. 49.1 years, P <0.02; and 49.0 vs. 51.6 years, P <0.001, respectively). Excluding women who developed ovarian cancer at ages younger than 30 and 35 years did not eliminate the association of ovarian cysts, functional cysts, or endometriosis with a lower mean age for ovarian cancer when compared with controls (P <0.05 for all comparisons). Women who had a hospital discharge diagnosis of endometriosis had a lower overall risk for development of endometrial cancer. There was no association seen with the diagnosis of benign or functional ovarian cyst with later cancer of the breast or cervix.