Consideration of factors of low accrual and methods for setting appropriate accrual periods: Japan Clinical Oncology Group study.

BACKGROUND

Poor patient accrual can delay reporting of clinical trials and, consequently, the development of new treatments. For reducing the risk of additional resource requirements, a method for setting planned accrual periods with minimal deviation from the actual accrual periods is desirable. Risk factors for poor patient accrual and the appropriate method of estimating the required accrual period for timely completion of clinical trials were evaluated using the data of trials conducted by the Japan Clinical Oncology Group.

METHODS

The study included 199 trials that started patient accrual between January 1, 1990, and June 30, 2021. The explanatory variables included factors that could be evaluated prior to trial commencement. We also evaluated whether the estimation methods for accrual pace could lead to completion within the planned accrual period.

RESULTS

Approximately 23.6% of trials were completed within the planned accrual period. The risk factors for trial extension included planned accrual periods > 3 years (reference group: ≤ 3 years, odds ratio [OR] 0.37, 95% confidence interval [CI]: 0.15-0.92, P = 0.033) and stratified trial design (reference group: nonrandomized phase II trials, nonrandomized phase III trial [OR: 3.28, 95% CI: 0.99-10.9, P = 0.051], randomized phase II trial [OR: 3.91, 95% CI: 0.75-20.30, P = 0.105], and randomized phase III trial [OR: 9.29, 95% CI: 3.39-25.40, P < 0.001]). The method of estimating the accrual pace based on past clinical trials facilitated timely completion of the trial (OR: 3.51; 95% CI: 1.73-7.10, P < 0.001), unlike the estimation method based on survey evaluation of the accrual pace for participating institutions (OR: 1.12, 95% CI: 0.56-2.26, P = 0.751). Furthermore, the discrepancy between planned and actual accrual periods was minimal when using the methods of considering the accrual pace of past clinical trials.

CONCLUSIONS

Considering the accrual pace of past clinical trials is useful for estimating the required accrual period if data from past trials are available. When conducting a survey, it is necessary to be cautious of overestimating the cases at each facility.