Introduction Endometriosis treatment is individualized and varies among patients. Studies suggest that hormonal suppression is protective against re-intervention and malignant transformation, however, they are largely based on self-reported diagnoses of endometriosis. We investigated patients with pathology proven endometriosis to characterize current management and determine whether hormone therapy reduces the risk of malignancy.

Methods Patients included had pathologically confirmed endometriosis diagnosed in British Columbia from 2000–2008 (n=4411). Data was linked to health administration holdings through Popdata BC.

Results After surgery, 475 (10.8%) patients received unopposed estrogen, 1567 (35.5%) estrogen and progesterone and 423 (9.6%) progesterone alone (p<0.001). 408 (9.3%) used GnRH agonists or antagonists. 194 (4.4%) patients were diagnosed with ovarian cancer; 68 (1.6%) with endometrioid and 58 (1.3%) with clear cell histology. There were 30 cancers diagnosed more than 6 months following index surgery. Those with ovarian cancer were less likely to have a prior physician visit coded for endometriosis (11% versus 34%; p<0.001) and were more likely asymptomatic (34.6% with prior visits for pelvic pain versus 51.4% ;p<0.001). Patients with malignancy were less likely to have been prescribed hormonal suppression prior to surgery, 13% with OCP use and 1.9% with GnRH agonist use compared to 36% and 10% respectively in benign endometriosis (p<0.001 for both medications).

Conclusion/Implications The majority of patients in our cohort were not placed on hormonal suppression after a pathology proven diagnosis of endometriosis. This study suggests early diagnosis and treatment of endometriosis may be protective against malignant transformation however a larger study is required.