Why most patients with advanced cancer never reach a clinical trial

Clinical takeaway: Discuss clinical trial eligibility early and proactively with patients who have advanced cancer. Access to trials appears to depend not only on patient factors, but also on the physician, practice infrastructure, and local research culture.

Clinical trials are essential for advancing cancer care, yet participation remains low despite widespread patient willingness to enroll when offered the opportunity. Historically, efforts to improve enrollment have focused on patient-level barriers, but this study suggests structural factors within oncology practices may have a greater influence on who ultimately gains access.

In a cohort study, investigators analyzed 205,743 adults with advanced or metastatic cancer treated by 1,664 physicians across 107 predominantly community-based US oncology practices between 2011 and 2024. Overall, only 5.2% of patients participated in a clinical trial, although enrollment increased from 3.9% in 2011 to 6.8% in 2024.

Participation was highly concentrated among a small group of physicians and practices. Just 23% of physicians accounted for 84% of all trial enrollments, while about 20% of practices accounted for 81% of enrolled patients. Nearly 30% of physicians did not enroll a single patient during the study period.

Importantly, physician- and practice-level factors explained more variation in trial participation than patient characteristics. Practice-level factors accounted for 15% of the variation, compared with 12% for physician factors and 11% for patient factors. The influence of physicians and practices increased over time, while the contribution of patient characteristics declined.

Patients treated by highly subspecialized oncologists (those focused on one to four cancer groups) had roughly two to four times the odds of participating in a trial. Patients whose physicians had enrolled trial participants in the previous 2 years had 58% higher odds of participating in a trial. Treatment at highly research-engaged practices was associated with nearly threefold greater odds of participation, whereas practices serving large numbers of socioeconomically disadvantaged patients had 58% lower odds.

In an accompanying editorial, Raymond U. Osarogiagbon, MBBS, of Baptist Cancer Center, wrote that the study “shine[s] a light on where we need to seek solutions.”

Sources: Jiang C, et al. (2026 Oct 6) JAMA Netw Open. Physician- and practice-level variation in clinical trial participation among patients with advanced cancer