Feasibility of Cancer Clinical Trial Enrollment Goals Based on Cancer Incidence

More than 20% of US clinical trials fail to accrue sufficiently. Our purpose was to provide a benchmark for better understanding clinical trial enrollment feasibility and to assess relative levels of competition for patients by cancer diagnosis.

The Database for Aggregate Analysis of ClinicalTrials.gov, up to date as of September 3, 2017, was used to identify actively recruiting, interventional oncology trials with US sites. Observational studies were excluded because not all are registered. Trials were categorized through Medical Subject Headings or free-text condition terms and sorted by cancer diagnosis. Trials that included more than one cancer diagnosis were included in the overall cohort but excluded when evaluating enrollment by cancer type. Trial enrollment slot availability was estimated between September 1, 2017, and August 31, 2018. Availability was estimated from total anticipated enrollment and duration, assuming a constant recruitment rate. Estimates for studies with both foreign and domestic sites were then prorated to calculate available enrollment in the United States alone. Ratios of the number of newly diagnosed patients in the United States available per trial slot were estimated using the American Cancer Society cancer incidence estimates for 2017.

A total of 4,598 interventional oncology trials were identified. Overall, the estimated ratio of newly diagnosed patients available per trial slot was 12.6. Estimated ratios of patients per trial slot for six cancer diagnoses with the highest potential of 12-month US enrollment were as follows: colorectal, 24.7; lung and bronchus, 20.1; prostate, 17.6; breast (female), 13.8; leukemia, 11.6; and brain and other nervous system, 6.0.

For all cancers, successfully accruing trials currently open would require that more than one in every 13 recently diagnosed patients (7.9%) enroll. This ratio and relative difficulty of accrual varies among cancers examined.