Rapid Fire Oral Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Ovarian cancer prognosis in women with a history of endometriosis: differences by endometriosis subtype (146208)

Amandi Hiyare Hewage 1 , Martin Healey 2 3 , Tanya Ross 1 , Peter Grant 2 , Susan Jordan 4 , Yael Naaman 3 , Penelope M Webb 1 , Ingrid Rowlands 1
  1. Population Health Program, QIMR Berghofer, Herston, Queensland , Australia
  2. Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Carlton, Victoria, Australia
  3. The Royal Women’s Hospital, Parkville, Victoria, Australia
  4. School of Public Health, The University of Queensland, Brisbane, Queensland , Australia

Aims
Although endometriosis is a risk factor for ovarian cancer, its effect on ovarian cancer prognosis and the potential differences by endometriosis subtypes are unclear. We compared overall survival among women with epithelial ovarian cancer with and without a history of endometriosis and examined survival by endometriosis subtype.

 

Methods
Records for Australian women diagnosed with ovarian cancer between 1984 and 2020 were linked to administrative health datasets using probabilistic linkage. Endometriosis in these women was ascertained using hospital diagnosis and Medicare codes. Descriptive statistics were used to compare characteristics of women with and without an endometriosis record. Survival was measured from ovarian cancer diagnosis until death or last-known service date. Survival models, stratified by ovarian cancer histotype, were used to estimate whether an endometriosis diagnosis was associated with all-cause mortality.  

 

Results
Among 25,250 eligible women, 1,840 (7.3%) had a record of endometriosis. Women with endometriosis were younger at ovarian cancer diagnosis than those without endometriosis (53 vs 63 years). In crude analyses, endometriosis was associated with better overall survival (HR=0.43, 95% CI: 0.40–0.46) but the association was attenuated after adjustment for age, year and state of diagnosis (aHR=0.70, 95% CI: 0.65–0.75). The survival difference was greatest within the first two years after ovarian cancer diagnosis and became less pronounced with increasing follow-up time. Overall survival also varied by endometriosis subtype with those with endometrioma and superficial endometriosis having better survival than those with deep infiltrating endometriosis (aHR= 0.70 and 0.69 vs 0.89 respectively). Associations were broadly consistent across serous, endometrioid, and clear cell ovarian cancer histotypes.

 

Conclusions

These findings suggest heterogeneity in ovarian cancer prognosis according to endometriosis history and subtype. The survival advantage may reflect younger age at diagnosis, but further investigation is needed to clarify the roles of endometriosis biology and other patient factors in shaping survival outcomes.