Endometriosis-associated ovarian cancer: a different clinical entity

Objective: To compare survival outcomes and patterns of recurrence between endometriosis-associated ovarian cancer patients and non-endometriosis-associated ovarian cancer patients. Methods: This retrospective study included data of consecutive patients with endometrioid or clear cell ovarian cancer treated at the Fondazione IRCCS Istituto Nazionale dei Tumori di Milano between January 2010 and June 2021. Patients were assigned to one of two groups according to the absence or presence of endometriosis together with ovarian cancer at final histological examination. Survival outcomes were assessed using Kaplan-Meier and Cox hazard models. Proportions in recurrence rate and pattern of recurrence were evaluated using the Fisher exact test. Results: Overall, 83 women were included in the endometriosis-associated ovarian cancer group and 144 in the non-endometriosis-associated ovarian cancer group, respectively. Patients included in the non- endometriosis-associated ovarian cancer group had a shorter disease-free survival than those in the endometriosis-associated ovarian cancer group (23.4 (range 2.0-168.9) vs 60.9 (range 4.0-287.8) months; p<0.001). Univariable and multivariable analyses showed that the association with endometriosis, previous hormonal treatment, early stage at presentation, and endometrioid histology were related to better disease-free survival in the entire study population. Similarly, patients in the non-endometriosis-associated ovarian cancer group had a shorter median (range) overall survival than those in the endometriosis-associated ovarian cancer group (54.4 (range 0.7-190.6) vs 77.6 (range 4.5-317.8) months; p<0.001). Univariable and multivariable analyses showed that younger age at diagnosis, association with endometriosis, and early stage at presentation were related to better overall survival. The recurrence rate was higher in the non-endometriosis-associated ovarian cancer group (63/144 women, 43.8%) than in the endometriosis-associated ovarian cancer group (17/83 women, 20.5%; p<0.001). Conclusions: Endometriosis-associated ovarian cancer patients had significantly longer disease-free survival and overall survival than non-endometriosis-associated ovarian cancer patients, while the recurrence rate was higher in non-endometriosis-associated ovarian cancer patients.