Geographic disparities, trial characteristics, and transparency of 3720 ovarian cancer clinical trials

To evaluate the trial characteristics, transparency, and geographic accessibility of ovarian cancer clinical trials registered on ClinicalTrials.gov from 2000 to 2025; identify major reasons for trial termination; and estimate state-level enrollment-to-incidence ratios across the United States (U.S.).

We conducted a longitudinal analysis of interventional ovarian cancer clinical trials initiated between January 1, 2000, and December 31, 2025. Trial characteristics, funding sources, transparency indicators, and reasons for termination were extracted from ClinicalTrials.gov. Comparisons were performed between U.S. and non-U.S.

State-level ovarian cancer trial enrollment-to-incidence ratios in the U.S. were calculated.

A total of 3720 ovarian cancer clinical trials were included in the analysis (1891 U.S.-based and 1829 non-U.S.-based). Most trials were treatment-focused (78.5%), drug-based (70.1%), employed single-arm or parallel-group designs (86.2%), and were early phase (60.8%). The majority were open-label (82.3%), and 8.8% explicitly indicated an intention to share individual participant data. Among eligible completed trials, 31.4% had posted results on ClinicalTrials.gov. Compared with non-U.S. trials, U.S. trials were more frequently early phase (75.2% vs. 45.9%), single-arm (46.4% vs. 39.5%), and drug-based (74.6% vs. 65.4%) (all P-value< 0.001). Large numbers of trials were terminated, most commonly attributed to recruitment difficulties (27.3%), sponsor decisions (25.2%), and efficacy-related concerns (13.0%). The overall estimated trial enrollment-to-incidence ratio is 12.6%. Geographic information system (GIS) analyses demonstrated substantial geographic heterogeneity in trial enrollment to incidence ratio estimates, with state-level estimates ranging from 4.7% in Arkansas to 67.5% in the District of Columbia.

This analysis identifies substantial heterogeneity in ovarian cancer clinical trial design, transparency, and geographic distribution of enrollment. Strengthening trial design rigor, improving compliance with results reporting and data-sharing requirements, and adopting more geographically inclusive recruitment strategies are important steps to enhance the transparency, efficiency, and representativeness of the clinical research infrastructure.