Objectives: Neoadjuvant chemotherapy (NACT) is an increasingly common primary treatment in advanced ovarian cancer. This study assessed real-world treatment patterns in advanced ovarian cancer using an electronic health record (EHR)-derived national database evaluated differences in treatment modality according to demographic characteristics, described specific chemotherapeutic agents and regimens used in NACT, and examined differences in treatment duration and time to next treatment. Methods: This retrospective study of patients diagnosed with tubal, peritoneal, or ovarian cancer between January 1, 2011, and March 31, 2020, was conducted using the US nationwide Flatiron Health EHR- derived de-identified database. Patients were included if they had a confirmed new diagnosis of advanced (stage III or IV) ovarian cancer and received chemotherapy or surgery as their initial treatment within 90 days of diagnosis. Patients' demographics were described and compared by treatment groups using ANOVA or Chi-square tests. Rates of initial treatment with surgery or chemotherapy were calculated. Time to next treatment (TTNT) was calculated from the start of initial treatment to the start of second-line therapy or death and censored at the date of the last confirmed visit. TTNT was estimated using Kaplan Meier curves with a 3-month landmark. Results: Our final cohort included 2917 patients. Sixteen percent of the total cohort (481 patients) received chemotherapy only without surgical intervention, and 10% (291 patients) received only surgery. The overall mean age was 65 years, with NACT patients being slightly older (67.5 vs 63.6 years, p<0.001). Although Black and Hispanic patients had equal proportions undergoing NACT versus primary cytoreductive surgery (PCS), a greater proportion of White (55% vs 44%) and Asian (69 vs 30%) patients received PCS. More NACT patients had an ECOG score of 2/3/4 (59% vs 40%, p<0.001), and more patients receiving PCS were treated at an academic center (62% vs 37%, p=0.08). NACT use as primary treatment increased from 26% in the first quarter of 2011 to 61% in the first quarter of 2020. Among the 1323 patients who received chemotherapy first, the most common regimen was carboplatin and paclitaxel (74%), followed by carboplatin, paclitaxel, and bevacizumab (14%). The remaining 12% of patients received non-standard chemotherapy regimens, including docetaxel, liposomal doxorubicin, gemcitabine, pemetrexed, cisplatin, abraxane, or a poly(ADP)ribose polymerase (PARP) inhibitor. The unadjusted median time to the next treatment was longer for PCS compared to NACT patients (13.8 vs 10.3 months). Conclusions: In this real-world population, NACT is becoming increasingly common, with the majority of advanced-stage patients receiving NACT. Time to next treatment was longer for patients receiving PCS, and NACT regimens are heterogeneous in chemotherapeutic agents used. These results provide insight into the shifting treatment patterns for patients over the last decade, which likely impacts patient counseling and healthcare utilization. [ABSTRACT FROM AUTHOR]