Clinical factors associated with prognosis in low-grade serous ovarian carcinoma: experiences at two large academic institutions in Korea and Taiwan.

Low-grade ovarian serous carcinoma (LGSOC) has clinical features different from high-grade serous ovarian carcinoma (HGSOC) accounting for the majority of epithelial ovarian cancer. Because of its rarity, previous studies have only focused on the high-grade disease without considering the differences between the two subtypes. This study aimed to evaluate the effect of the clinical prognostic factors known for HGSOC on survival in patients with LGSOC. Based on the Federation of Gynecology and Obstetrics (FIGO) stage, progression-free survival (PFS) was markedly decreased in advanced disease compared with early disease. For stage I, patients with stage IC had poorer survival than those with stage IA and IB regardless of the number of cycles of adjuvant chemotherapy. For advanced disease, no gross residual disease after primary cytoreductive surgery was significantly associated with longer PFS when compared with gross residual disease. In multivariate analysis for PFS and overall survival (OS), age, preoperative CA-125, time interval from surgery to chemotherapy, and the number of cycles of adjuvant chemotherapy were not associated with prognosis. Complete cytoreduction was the only independent prognostic factor for PFS (HR 2.45, p = 0.045). Our study revealed that the known prognostic factors in HGSOC did not show any effect on the survival in LGSOC except for FIGO stage and complete cytoreduction.