Most Advanced Cancer Trial Enrollment Comes From a Small Share of Oncologists

Clinical trial participation among patients with advanced cancer increased moderately but remained low from 2011 to 2024, and enrollment was concentrated among a small share of physicians and practices, according to a retrospective cohort study published in JAMA Network Open.

Investigators used the Flatiron Health Research Database to examine 205,743 adults with advanced or metastatic solid tumors treated by 1664 physicians at 107 trial-available US oncology practices. Trial participation was defined as receipt of a clinical study drug. Mixed-effects models estimated how much variation in participation was attributable to patient-, physician-, and practice-level factors.

Overall, 10,785 patients (5.2%) participated in a trial, with the annual rate rising from 3.9% in 2011 to 6.8% in 2024. A total of 389 physicians (23.4%) accounted for 83.6% of enrollments, 21 practices (19.6%) accounted for 80.5%, and 494 physicians (29.7%) enrolled no patients. Physician-level (12.3%) and practice-level (15.1%) factors explained more of the variation than observable patient-level characteristics (11.4%), and in exploratory analyses by diagnosis period, the practice-level share rose from 13.7% to 21.9%.

In multivariable analyses, higher odds of participation were associated with physician subspecialization (treating 1-2 vs more than 4 cancer groups: odds ratio [OR], 4.11; 95% CI, 2.53-6.68), physician trial enrollment in the 2 previous years (OR, 1.58; 95% CI, 1.43-1.76), and high practice research engagement (OR, 2.68; 95% CI, 2.12-3.39). Practices with the most socioeconomically disadvantaged patient populations had lower odds (OR, 0.42; 95% CI, 0.26-0.69), as did Black patients compared with White patients (OR, 0.74; 95% CI, 0.62-0.88).

The authors noted that the database primarily represents community oncology settings, that the study-drug definition likely underestimated enrollment, and that eligibility data were unavailable. Because physician and practice measures were derived from aggregated patient data, they cautioned against interpreting them as independent causal factors. They concluded that the findings suggest improving patient access to trials "requires efforts that extend beyond patient-level barriers to target physician behaviors and organizational structures."

Source: Jiang C, Lu CA, Liao JM, et al. Physician- and practice-level variation in clinical trial participation among patients with advanced cancer. JAMA Netw Open. 2026;9(10):e2633046. doi:10.1001/jamanetworkopen.2026.33046