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Endometriosis and Overall Risk of Breast Cancer

Obstet Gynecol; ePub 2016 Oct 6; Farland, et al

Laparoscopically-confirmed endometriosis was not associated with overall risk of breast cancer, however, it was significantly associated with an increased risk of estrogen receptor-positive/progesterone receptor-negative (ER+/PR-) breast tumors, a recent study showed. The prospective cohort study included 116,430 women from the Nurses’ Health Study II and followed from 1989 to 2013. Researchers found:

  • 5,389 (5%) women at baseline reported laparoscopically-confirmed endometriosis.
  • Over 24 years follow-up, 4,979 (3%) incident breast cancer cases were diagnosed.
  • Women with endometriosis were not at higher risk for overall (adjusted HR, 0.96), premenopausal (aHR, 1.05), or postmenopausal breast cancer (aHR, 0.93).
  • Women with endometriosis reported 2.87 ER+/PR- breast cancer cases per 10,000 person-years compared with women without endometriosis, resulting in nearly a 2-fold increased risk of ER+/PR- breast cancers (aHR, 1.90).


Farland LV, Tamimi RM, Eliassen H, et al. Laparoscopically confirmed endometriosis and breast cancer in the Nurses’ Health Study II. [Published online ahead of print October 6, 2016]. Obstet Gynecol. doi:10.1097/AOG.0000000000001684.