Should Cancer Trial Eligibility Become More Inclusive?

Patients with treatment-refractory cancers who did not meet eligibility criteria for a pan-cancer clinical trial but received waivers allowing them to participate had similar outcomes to patients who participated without waivers, a new analysis revealed.

The study, published online in Clinical Cancer Research, highlighted the potential benefits of broadening eligibility criteria for clinical trials.

“It is well known that results in an ‘ideal’ population do not always translate to the real-world population,” senior author Hans Gelderblom, MD, chair of the Department of Medical Oncology at the Leiden University Medical Center, Leiden, the Netherlands, said in a press release. “Eligibility criteria are often too strict, and educated exemptions by experienced investigators can help individual patients, especially in a last-resort trial.”

Although experts have expressed interest in improving trial inclusivity, it’s unclear how doing so might impact treatment safety and efficacy.

In the Drug Rediscovery Protocol (DRUP), Gelderblom and colleagues examined the impact of broadening trial eligibility on patient outcomes. DRUP is an ongoing Dutch national, multicenter, pan-cancer, nonrandomized clinical trial in which patients are treated off-label with approved molecularly targeted or immunotherapies.

In the trial, 1019 patients with treatment-refractory disease were matched to one of the available study drugs based on their tumor molecular profile and enrolled in parallel cohorts. Cohorts were defined by tumor type, molecular profile, and study drug.

Among these patients, 82 patients — 8% of the cohort — were granted waivers to participate. Most waivers (45%) were granted as exceptions to general- or drug-related eligibility criteria, often because of out-of-range lab results. Other categories included treatment and testing exceptions, as well as out-of-window testing. 

The researchers then compared safety and efficacy outcomes between the 82 participants granted waivers and the 937 who did not receive waivers. 

Overall, Gelderblom’s team found that the rate of serious adverse events was similar between patients who received a waiver and those who did not: 39% vs 41%, respectively.

A relationship between waivers and serious adverse events was deemed “unlikely” for 86% of patients and “possible” for 14%. In two cases concerning a direct relationship, for instance, patients who received waivers for decreased hemoglobin levels developed anemia.

The rate of clinical benefit — defined as an objective response or stable disease for at least 16 weeks — was similar between the groups. Overall, 40% of patients who received a waiver (33 of 82) had a clinical benefit vs 33% of patients without a waiver (P =.43). Median overall survival for patients that received a waiver was also similar — 11 months in the waiver group and 8 months in the nonwaiver group (hazard ratio, 0.87; P =.33).

“Safety and clinical benefit were preserved in patients for whom a waiver was granted,” the authors concluded.

The study had several limitations. The diversity of cancer types, treatments, and reasons for protocol exemptions precluded subgroup analyses. In addition, because the decision to grant waivers depended in large part on the likelihood of clinical benefit, “it is possible that patients who received waivers were positively selected for clinical benefit compared with the general study population,” the authors wrote.

So, “although the clinical benefit rate of the patient group for whom a waiver was granted appears to be slightly higher, this difference might be explained by the selection process of the central study team, in which each waiver request was carefully considered, weighing the risks and potential benefits for the patient in question,” the authors explained.

Overall, “these findings advocate for a broader and more inclusive design when establishing novel trials, paving the way for a more effective and tailored application of cancer therapies in patients with advanced or refractory disease,” Gelderblom said.

Commenting on the study, Bishal Gyawali, MD, PhD, said that “relaxing eligibility criteria is important, and I support this. Trials should include patients that are more representative of the real-world, so that results are generalizable.”

However, “the paper overemphasized efficacy,” said Gyawali, from Queen’s University, Kingston, Ontario, Canada. The sample size of waiver-granted patients was small, plus “the clinical benefit rate is not a marker of efficacy.”

“The response rate is somewhat better, but for a heterogenous study with multiple targets and drugs, it is difficult to say much about treatment effects here,” Gyawali added. Overall, “we shouldn’t read too much into treatment benefits based on these numbers.”

Funding for the study was provided by the Stelvio for Life Foundation, the Dutch Cancer Society, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, BristolMyers Squibb, pharma&, Eisai Co., Ltd., Ipsen, Merck Sharp & Dohme, Novartis, Pfizer, and Roche. Gelderblom declared no conflicts of interest, and Gyawali declared no conflicts of interest related to his comment.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.