Objective The aim of this study was to identify risk factors for progression to invasive carcinoma in patients with borderline ovarian tumors (BOTs).

Methods We performed a retrospective review of all patients treated and followed for BOTs between 1996 and 2011. Multivariate Cox proportional hazards model analysis was performed to identify independent risk factors for progression to invasive carcinoma.

Results A total of 364 patients were identified. During the median follow-up of 53.8 months, 31 patients (8.5%) developed recurrent disease: 12 (3.3%) had recurrent disease with progression to invasive carcinoma, and 19 (5.2%) had recurrent disease with borderline histology. Disease-related deaths (7/364; 1.7%) were observed only in patients with progression to invasive carcinoma. The multivariate analysis showed that independent risk factors for progression to invasive carcinoma were advanced disease stage (hazard ratio [HR], 5.59; P = 0.005), age 65 years or older (HR, 5.13; P = 0.037), and the presence of microinvasion (HR, 3.71; P = 0.047). These 3 factors were also independently related to overall survival.

Conclusions Although patients with BOTs have an excellent prognosis, the risk of progression to invasive carcinoma and thereby death remains. Therefore, physicians should pay closer attention to BOT patients with these risk factors (ie, advanced disease stage, old age, and microinvasion), and more careful surveillance for progression to invasive carcinoma is needed.