Borderline ovarian tumors (BOTs) are estimated to comprise 10%-15% of all epithelial tumors of the ovary. They are characterized by their behavior, which falls somewhere between benign ovarian masses and frank carcinomas. They have cytologic characteristics suggesting malignancy, such as higher cellular proliferation and more variable nuclear atypia, but, unlike carcinomas, they lack destructive stromal invasion. For decades after their recognition by the International Federation of Gynecology and Obstetrics in 1971, these tumors were classified as being of low malignant potential (and subsequently referred to as LMP tumors of the ovary). Beginning with the 2014 World Health Organization classification, the recommended terminology is now borderline tumor of the ovary.
The primary treatment for BOTs is surgery. With a mean age at diagnosis in the fifth decade, many patients with BOTs desire ovarian preservation to maintain fertility and/or prevent surgical menopause. This raises multiple questions regarding the use of fertility-sparing surgery for BOTs: What types of procedures are safe and should be offered? For those patients who undergo fertility-sparing surgery initially, is additional surgery indicated after completion of childbearing or at an age closer to natural menopause? What should this completion surgery include?
The diagnosis of a BOT is frequently only confirmed after the decision for ovarian conservation has been made. What should be considered before electing to proceed with ovarian cystectomy instead of unilateral salpingo-oophorectomy (USO)?
Is the risk of recurrence higher with cystectomy versus oophorectomy?
Yes. The risk of recurrence of BOT appears to be higher after cystectomy than it is after oophorectomy. There is a large range reported in the literature, with the risk of recurrence after cystectomy described as between 12% and 58%. Most studies report recurrences between 25% and 35% of patients who undergo cystectomy. In contrast, the risk of recurrence after USO is often reported to be approximately 10%. Higher risk of recurrence after cystectomy is speculated to be due to leaving some BOT at the time of initial surgery.
Multiple meta-analyses have found an increased risk of recurrence after cystectomy. The risk of recurrence after unilateral cystectomy was 19.4%, compared with 9.1% after USO, in 2,145 patients included in a 2017 meta-analysis.1 Similarly, a 2021 meta-analysis found a significantly higher rate of BOT recurrence in patients who underwent unilateral or bilateral cystectomy compared with USO (odds ratio, 2.02; 95% confidence interval, 1.59-2.57).2
Does the higher recurrence risk translate into a difference in long-term outcomes?
No. Despite an increased risk of recurrence after cystectomy, ovarian-sparing surgery does not appear to alter patients’ survival. The pooled mortality estimate was 1.6% for those undergoing fertility-sparing surgery (95% CI, 0.011-0.023), compared with 2.0% for those undergoing radical surgery (95% CI, 0.014-0.029), in a 2015 meta-analysis of over 5,100 patients. The analysis included studies in which patients underwent unilateral cystectomy, bilateral cystectomy, USO, or USO plus contralateral cystectomy. The low mortality rate did not allow for comparison between the different types of fertility-sparing surgeries.3