Researchers identified characteristics that may lead to low patient accrual for a clinical trial, according to a study published in the JNCI: Journal of the National Cancer Institute (doi:10.1093/jnci/djv416).

Nearly 1 in 4 publicly sponsored cancer clinical trials fail to enroll enough participants to draw valid conclusions about treatments or techniques. These trials represent a misuse of scarce human and economic resources and contribute little to medical knowledge.

The perceived barriers to accrual from the patient or provider perspective have been investigated in studies; however, very few examined the trials themselves to determine why some trials are able to accrue patients faster than expected while others fail to attract even a fraction of the intended number of participants.

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Researchers from the University of Washington and the Fred Hutchinson Cancer Research Center analyzed information on 787 phase II/III clinical trials sponsored by the National Clinical Trials Network (NCTN) launched between 2000 and 2011.

The researchers found that 145 (18%) of NCTN trials closed with low accrual or had less than 50% of target accrual 3 years or more after opening. They excluded trials that closed because of toxicity or interim results.

A review of the literature and interviews with clinical trial experts revealed multiple trial-level factors that were associated with poor accrual to NCTN trials. Those risk factors included increased competition for patients from currently ongoing trials, planning to enroll a higher proportion of the available patient population, and not evaluating a new investigational agent or targeted therapy.

The researchers then developed a multivariable prediction model of low accrual using 12 trial-level risk factors. Their prediction model demonstrated good agreement between predicted and observed risks of low accrual in a preliminary validation using 46 trials opened between 2012 and 2013.

“Systematically considering the overall influence of these factors could aid in the design and prioritization of future clinical trials,” concluded the researchers. They stated that this research provides a response to the recent directive from the Institute of Medicine to “improve selection, support, and completion of publicly funded cancer clinical trials.”

In an accompanying editorial (JNCI; doi:10.1093/jnci/djv379), Derek Raghavan, MD, of Levine Cancer Institute in Charlotte, North Carolina, stated that the focus should be on getting more patients involved in trials.

“We should strive to improve trial enrollment, giving the associated potential for improved results,” wrote Raghavan. “Whether the basis is incidental, because of case selection bias, or reflects the support available to trial patients has not been determined, but the fact remains that outcomes are better.”