Friend or foe? The prognostic role of endometriosis in women with clear cell ovarian carcinoma. A UK population-based cohort study

PURPOSE: The prognostic role of endometriosis amongst women with ovarian clear cell carcinoma (OCCC) remains debatable. The aim of this study was to ascertain the effect of endometriosis on the prognosis of OCCC. METHODS: A retrospective review of the medical records of 94 women diagnosed and treated for OCCC at a tertiary gynaecological cancer centre in the UK, spanning the period 2010-2019. Women were divided into two groups according to the presence of endometriosis. Clinico-pathological characteristics, progression-free survival (PFS) and overall survival (OS) were collated between the two groups. RESULTS: Forty-six cases of endometriosis-free OCCC (Ef-OCCC) were collated with 48 cases of endometriosis-related OCCC (Er-OCCC). There was no significant difference between the two groups regarding age (p-value = 0.2), FIGO stage (p-value = 0.8), residual disease (RD) (p-value = 0.07), adjuvant chemotherapy agent (p-value = 0.4) or chemo-resistance (p-value = 0.9). The presence of endometriosis did not significantly affect either OS or PFS. The median OS in the Ef-OCCC and Er-OCCC was 55.00 (95% CI 32.00-189.00) and 71.00 (95% CI 47.00-97.00; log rank = 1.35, p-value = 0.2) months. The median PFS in the Ef-OCCC and Er-OCCC group was 39.00 (95% CI 19.00-143.00) and 39.00 (95% CI 19.00-62.00; log rank = 0.7, p-value = 0.4) months. Survival differences between the two groups were not significant after stratification analysis for independent prognosticators. CONCLUSION: Endometriosis was not independently associated with the prognosis of OCCC either in crude analysis or after stratification for stage and RD. Further larger, well-designed prospective studies are warranted to draw firmer conclusions on the intrinsic link between endometriosis and OCCC.