Table 1_Cancer prevention and interception studies registered in ClinicalTrials.gov: a landscape analysis of trial characteristics and reporting gaps.xls

Associations between categorical variables were assessed using exact tests when appropriate.</p>Results<p>Among 209 eligible studies, 157 (75.1%) were interventional and 52 (24.9%) were observational. Most studies included adults and older adults, and 52.6% were classified as completed. Among interventional studies, randomized allocation and parallel-group designs predominated, while most studies were unmasked.

Gynecological and gastrointestinal malignancies were the most frequently represented cancer localizations. Funding was classified as ‘Other’ in most records, reflecting a heterogeneous registry category that could not be further disaggregated. Study type was associated with funding category (p = 0.028), whereas the association between study type and cancer localization was not statistically significant (p = 0.09, with a Cramér's V of 0.32).

Among interventional studies, 54 (34.4%) focused on early detection and diagnosis, aligning with the registry's ’Screening’ and ‘Diagnostic’ fields. Cancer interception and post-treatment disease control accounted for 52 studies (33.1%) but lacked distinct registry designations, while 51 (32.5%) addressed primary prevention and chemoprevention, corresponding to the ‘Prevention’ category.</p>Conclusions<p>Cancer prevention and interception research registered in ClinicalTrials.gov is heterogeneous and encompasses distinct clinical objectives.

Our findings highlight the need for explicit operational definitions and more granular, standardized reporting fields to improve the visibility, interpretability, and comparability of preventive oncology.</p>