Progress in the fight against cancer relies on being able to test new drugs and therapies in clinical trials. Yet, nearly 1 in 5 publicly funded cancer clinical trials fail to recruit enough participants to yield reliable results.

Share on Pinterest The researchers found that 18% of publicly funded cancer clinical trials close or fail to attract more than half their target number of patients.

“Such trials represent a waste of scarce human and economic resources and contribute little to medical knowledge,” note researchers, who have developed a mathematical tool to predict how difficult it might be to attract trial participants depending on a range of trial-specific factors.

The team, from the University of Washington and the Fred Hutchinson Cancer Research Center, both in Seattle, WA, writes about the new mathematical tool or algorithm – and how they arrived at it – in the Journal of the National Cancer Institute.

To develop the algorithm, the team first trawled through trials published in the last few years and identified several trial-related “risk factors” that are linked to low patient accrual rates.

They found, for instance, that trials requiring patients to give a tissue sample or undergo biopsy to decide if they can enroll tend to find it harder to attract participants than those that do not have such invasive eligibility tests.

Another risk factor is that when patients know they are not going to be – or are unlikely to be – treated with a potentially new drug or therapy, they are less likely to sign up.

First author Dr. Carrie Bennette, an investigator with the Hutchinson Institute for Cancer Outcomes Research (HICOR), says:

“If you have a trial looking at a new investigational drug, it’s much more likely to hit its accrual target.”

She explains this is especially true of phase 2 trials – the ones that test drug safety – which often guarantee participants will receive the new treatment.

However, this is not the case in phase 3 trials, whose purpose is to compare new treatments with the best currently available treatment. For this stage of drug testing, patients typically are randomly assigned to receive either cutting-edge, new therapies – albeit unproven – or approved treatments already in use.

This poses a dilemma; while randomization is essential for a phase 3 trial to yield reliable, robust evidence about how the new drug stacks up against the current therapy, it is this very factor that could make it less able to accrue trial participants. Dr. Bennette explains:

“As soon as you add in randomization, where patients may or may not get [the investigational treatment], it wipes away the higher accrual rates we found among trials studying new treatments.”