Borderline tumours of the ovary: A cohort study of the Arbeitsgmeinschaft Gynakologische Onkologie (AGO) Study Group

Abstract Background Borderline ovarian tumours (BOTs) are recognised as a unique entity of ovarian tumours that do not exert infiltrative destructive growth or stromal invasion. Prognosis of BOT is much better compared to the more common invasive epithelial ovarian cancer. Information regarding prognostic factors is inconclusive and no prospective studies exist that evaluate therapeutic strategies. We therefore started a retrospective–prospective cohort study to better understand BOT and identify scenarios in which future studies could be developed. Methods Consecutive patients with BOT treated between 1998 and 2008 in 24 German centres were analysed. The retrospective part of the study retrieved patients’ data from hospital records and clinical tumour registries while active follow-up and an independent central pathology review were carried out prospectively. Findings BOT was confirmed in 950 patients, two thirds had serous BOT and 30.5% mucinous BOT. Most were diagnosed in stage I (82.3%); 7.6% and 10.1% had stages II and III, respectively. Overall, 74 patients (7.8%) experienced relapse and 43 (4.5%) died within the observation period. Multivariate analysis revealed higher stage, incomplete staging, tumour residuals, and organ preservation as independent prognostic factors for disease recurrence. Neither microinvasion nor micropapillary growth pattern showed any significant impact. Of 74 relapsed patients, 30% had malignant transformation to invasive ovarian cancer with five-year progression-free survival and overall survival of 12% and 50%, respectively. Interpretation Prognosis of BOT correlates with tumour-related as well as surgery-related factors. The balance between recurrence risk and organ preservation and fertility-sparing surgery is an important issue deserving further research.