EP23.39: Mucinous borderline ovarian tumours: a rationalisation for follow up in a specialist ovarian clinic

To analyse follow up data with regards to operative method, tumour recurrence, repeat operations and completion surgery in patients with MBOT; assess time within and frequency of follow up within the service; and proposal of a follow up schedule. Patients presenting postoperatively following surgical treatment of MBOT to a clinic with expert ultrasound examiners were collated into a database. Data was analysed using ultrasound reports from their visits, histological reports, and electronic patient records. 55 patients were analysed. 70% had unilateral salpingo-oophorectomy, 26% had a cystectomy, and 4% had another procedure (unilateral salpingectomy, opening of pelvic side wall). None had debulking surgery. Index procedures occurred from 1996-2022. There was one recurrence in a patient who had initially had a cystectomy, detected six years following the index procedure. Patients who had a USO had a median follow up duration of 66 months with a median follow up frequency of 7.55 months. 14 patients underwent a cystectomy, carried out 2012-2022 at a median age of 29.5 years. They were all operated on electively with counselling. Their median time in the service was 58.5 months with a median frequency of follow up every 6.4 months. 7 secondary procedures were performed (50%): 1 recurrence (USO- 6 years after index procedure), 1 repeat cystectomy, 1 USO (non-malignant cyst), 4 completion procedures (patient choice). 7/54 (13%) patients with MBOT have had cystectomy only and continue under long-term follow up with no recurrence. Accurate preoperative diagnosis of MBOT allows for more conservative surgical treatment with increasing numbers requiring long term follow up within a limited resource. Careful patient selection ensures cystectomy is a viable option especially for younger patients who may wish to retain their fertility. Expert sonographic opinion every 12 months for those who have had USO and every 6 months for those who have had a cystectomy may present a safe way to ensure long term follow up.