Low-grade serous ovarian carcinoma (LGSOC) is a rare histologic subtype of ovarian cancer, which accounts for less than 10 % of serous ovarian carcinomas and 5 % of epithelial ovarian cancer [[1], [2], [3], [4]]. It is characterized by an earlier age of onset, with a median age of 46.9 years, and a better prognosis than high-grade serous ovarian carcinoma (HGSOC) when discovered at advanced stages (median survival of 81 months for stages II/IV) [5]. Unlike HGSOC, LGSOC is relatively chemoresistant to platinum-based chemotherapy, with response rates for advanced-stage disease of about 10–20 % [6]. It is not linked to the BRCA 1/2 constitutional mutation and does not benefit from PARP inhibitors, further distinguishing its clinical profile [7,8].

Primary cytoreduction surgery (PCS) is the mainstay of LGSOC treatment [[9], [10], [11]]. The primary goal of PCS is to achieve complete cytoreduction, as residual disease (RD) after surgery is a key prognostic factor in ovarian cancers, including LGSOC. RD is typically assessed by the largest diameter of the remaining tumor post-surgery. Paradoxically, there is no universal consensus on the definition of “optimal” residual disease for LGSOC. The classification often follows the Completeness of Cancer Resection (CCR) score [12], which categorizes patients based on the amount of visible disease remaining after cytoreductive surgery: no visible disease (CC0), residual disease <2.5 mm (CC1), residual disease between ≥2.5 mm and ≤ 2.5 cm (CC2), and residual disease >2.5 cm (CC3). This scoring system provides a standardized way to evaluate surgical outcomes and prognostic implications. However, optimal RD has been variously defined, ranging from no macroscopic RD (R0) to residual tumor nodules measuring less than 1 cm or microscopic RD (R1) and macroscopic RD measuring more than 1 cm (R2). More recent data suggest that the most favorable survival outcomes are associated with complete cytoreduction and the absence of macroscopic residual disease (CC0 or R0) [13]. Furthermore, the variability in definitions of RD complicates comparison across studies, and detailed peritoneal cancer index (PCI) data are frequently lacking in the literature [14], further limiting the evaluation of disease burden and surgical outcomes.

Despite these advancements, significant uncertainties remain regarding the optimal timing of surgery. While PCS is the standard, the role of neoadjuvant chemotherapy (NAC) followed by interval debulking surgery (IDS) is debated, particularly in cases with extensive disease where achieving complete cytoreduction at initial surgery may be not feasible.

The aims of the study were to perform a systematic review of the literature and a meta-analysis to evaluate and quantify the prognostic impact of PCS compared with neoadjuvant chemotherapy followed by interval debulking surgery (NAC-IDS) and to assess the prognostic impact of RD after surgery on survival outcomes among patients with advanced-stage low-grade serous ovarian cancer.