Early termination of clinical trials enrolling patients with breast cancer: Reasons, determinants, and temporal patterns.

BACKGROUND

The occurrence of clinical trial termination before planned completion (or "early termination" [ET]) remains poorly characterized in the breast cancer field. This study investigates the reasons, determinants, and temporal patterns of ET in breast cancer trials.

METHODS

We conducted a cross-sectional study using the Aggregate Analysis of ClinicalTrials.gov (AACT) database, including breast cancer trials initiated between 2001 and 2025. Reasons for ET were identified and classified into predefined categories. Factors associated with ET were evaluated using multivariable logistic regression, and temporal patterns were assessed using competing risk analysis and a multivariable Fine-Gray subdistribution hazard model.

RESULTS

A total of 5251 trials were included. "Poor accrual" was the most common reason for ET (39.2%), followed by "sponsor decision or strategic reasons" (22.4%) and "operational or management issues" (13.4%). "Poor accrual" was the leading cause of ET among phase 2 and 3 trials, academic-sponsored studies, and single-center trials, whereas "sponsor decision or strategic reasons" predominated among phase 1 trials, industry-sponsored studies, and trials conducted globally. In multivariable logistic regression analyses, phase 2 trials had a higher likelihood of ET (OR = 1.48; P < .001), whereas multicenter studies (OR = 0.70; P < .001) and trials with non-treatment purposes (OR = 0.61; P < .001) had a lower likelihood of ET. Similar patterns were observed in the Fine-Gray model.

CONCLUSIONS

Early termination of breast cancer trials is a heterogeneous phenomenon, with distinct patterns based on study characteristics. Tailored strategies to improve trial feasibility, participant recruitment, and operational planning may reduce the risk of ET.