The Oncological Follow-Up of Fertility Sparing Surgery for Mucinous Borderline Ovarian Tumours: A Retrospective Cohort Study

<b>Background/Objectives</b>: To determine whether long-term oncological follow-up is required following fertility-sparing surgery (FSS) for mucinous borderline ovarian tumours (MBOTs). <b>Methods</b>: A retrospective cohort study set in the tertiary gynaecology oncology centre at Imperial College Healthcare NHS Trust. Patients included were those under follow-up post-surgery for an MBOT in the ovarian clinic from 2007 to 2025. Rate of recurrence was compared amongst patients who underwent ovarian cystectomy, unilateral salpingo-oophorectomy (USO) or bilateral salpingo-oophorectomy (BSO) +/- hysterectomy. <b>Results</b>: From 74 patients diagnosed with MBOT, 36.5% (27/74) underwent BSO +/- hysterectomy and 63.5% (47/74) had FSS. Of the patients who underwent FSS, 59.6% (28/47) had an initial USO and 40.4% (19/47) underwent ovarian cystectomy. Subsequently, 63.2% (12/19) of patients who initially had ovarian cystectomy proceeded with completion USO, leading to a total of 40 USOs performed. There were no recurrences following BSO +/- hysterectomy, primary USO or completion USO after a median follow-up of 49.0, 65.5 and 48.0 months, respectively. Of the patients who underwent ovarian cystectomy, 15.8% (3/19) were found to have residual MBOT (n = 1) two months post-cystectomy or MBOT recurrence (n = 2) at 10- and 66-months post-cystectomy, all diagnosed at USO. There is a significant association between ovarian cystectomy and disease recurrence (Fisher's exact test <i>p</i> = 0.015). <b>Conclusions</b>: Patients of reproductive age who undergo USO for a MBOT can be offered a reduced follow-up schedule as the risk of recurrence is very low. In contrast, patients who are managed by ovarian cystectomy have a higher risk of recurrence and require long-term surveillance monitoring.