What Accounts For Low Enrollment In Clinical Trials For Cancer Drugs?

What Accounts For Low Enrollment In Clinical Trials For Cancer Drugs?

Comments by DR Ryan This is a rather soft and not  in depth treatment of a national disgrace. The elderly are underrepresented in trials  but will have the fastest growing portion of the population and the most cancers .Lower socioeconomic communities are underrepresented, We are just waking up to the need to get minority ethnicities involved. There must be more enticement and ethical reward to get these trials down to the community oncologist.  Perhaps regional funding of data managers and nurses  who  travel some what as did Paul to spread the good word and collect the data and advertise the trials, How do you get doc’s in smaller pratices who represent 75% of all Oncologists concinvced to add this to their workload- well there are ways and I believe the American people should get smart fast. We have academic jewels throughout the nation but some are still not close enough- that distance needs to become less apparent. We have Altzeimers, Diabetes Mellitus, Cancer as #1 and Cardiovascualr disease ( include pulmonary and it is #1 )  as the entities we need to put more tax dollars to the fight  and we will save far more than we spend as less cases of fatal prolonged disease costing a fortune are less expensive than the cost that those top 4 will and are costing. We will net save lives and heartache and increase duration of meaningful life and PRODUCTIVE  life Dr Ryan

Emily Mullin ,


I write about the intersection of health and humanity.

Opinions expressed by Forbes Contributors are their own. I am a freelance science writer who seeks to explore the intersection of health and humanity. I have written about public and global health, neuroscience, genomics, regenerative medicine, aging, rare diseases, cancer and science policy, among other topics. I hold an MA in Science Writing from Johns Hopkins University, and my stories have appeared in The Washington Post, Smithsonian Magazine, The Atlantic, Baltimore Sun, Pacific Standard and U.S. News & World Report. Previously, I served as associate editor at FierceBiotech, where I covered drug discovery breakthroughs, preclinical research and R&D funding for the weekly industry newsletter FierceBiotechResearch. Before that, I was a reporter for the Baltimore Business Journal, where I covered healthcare and biotechnology. I am passionate about science literacy, SciArt and the integration of science and theater.

The author is a Forbes contributor. The opinions expressed are those of the writer.



Human clinical trials are an essential–and expensive–step in the drug development process. If an experimental therapy is found effective, it could replace the standard of care and provide new treatment options for patients.

But if a clinical trial fails to enroll enough participants, researchers aren’t able to draw meaningful conclusions about the intervention or drug studied in the trial because there’s just not a big enough sample size. A new study in the Journal of the National Cancer Institute found that this is happening with nearly one out of five publicly funded cancer clinical trials.

The authors of the report, from the Fred Hutchinson Cancer Research Center and the University of Washington, looked at data from 787 Phase II/III adult cancer trials launched between 2000 and 2011 that were sponsored by the National Cancer Institute’s National Clinical Trials Network, which includes leading academic institutions, community medical centers and other healthcare organizations as participating sites. Excluding trials that closed because of toxicity or interim results, the researchers found that 145 trials–or 18%–closed with low enrollment or were accruing at less than 50% of their target enrollment three years or more after the clinical trial began.

If a trial is stopped early or is not able to finish as planned because of poor accrual, researchers involved in the study cannot report any results of the trial.

Individuals must meet specific requirements, or eligibility criteria, to enroll in a clinical trial. Eligibility criteria vary from study to study and may include certain prerequisites like age, gender, medical history and current health status. Cancer trials usually require that patients have a particular type and stage of cancer. All of these factors limit which trial or trials prospective participants are able to sign up for.

Previous research has examined these barriers and others from both a patient perspective and healthcare provider standpoint. But this latest study identifies reasons why certain trials are able to accrue patients faster than expected while others aren’t able to attract even a fraction of the intended number of participants.

One major factor impacting whether patients sign up for a clinical trial is the likelihood that they will receive the treatment being tested. New experimental drugs are more likely to draw a higher number of patients, especially in Phase II trials, which test the efficacy of a drug in a bigger group of people than in an initial Phase I safety trial. In a Phase II trial, there is usually no placebo so all participants receive the treatment. However, different groups within the trial may get different doses or get the treatment in different ways to see which is safest and most effective. Accrual tends to drop in Phase III trials for new therapies because participants are randomized into treatment and placebo groups.


Another design element in clinical trials that could dissuade potential participants from joining is requiring an invasive procedure in order to qualify for the trial. For example, some cancer trials need to perform a biopsy to obtain a tissue sample in order to determine whether patients are even eligible for the trial. Many biopsies use a fine needle, but sometimes surgery may be needed to get an appropriate tissue sample. Many individuals are reluctant to go through such a procedure if there’s no guarantee that they’ll be able to be in a study.

Other issues that account for low accrual are that trial organizers face increased competition for patients from currently ongoing trials, and they may also plan to enroll a higher proportion of the available patient population than they are realistically able to recruit.

Taking these risk factors and others into consideration, the researchers developed an algorithm to help predict patient accrual in cancer clinical trials. They hope the tool could eventually aid in the design and prioritization of future clinical trials.

Emily Mullin is a DC-based science writer, focusing on health and medicine. Follow her at Forbes and on Twitter.


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