Physician and Practice Factors Shape Advanced Cancer Trial Enrollment

Physician- and practice-level factors may have a greater influence on clinical trial participation among patients with advanced cancer than individual patient characteristics, according to a retrospective analysis of US oncology practices.^1,2

The study, published in JAMA Network Open, evaluated clinical trial participation among 205,743 adults with advanced or metastatic cancer treated by 1664 physicians across 107 US oncology practices between 2011 and 2024. Overall, 10,785 patients (5.2%) participated in a clinical trial, with enrollment increasing from 3.9% in 2011 to 6.8% in 2024.

Despite this increase, participation remained highly concentrated. Of the 1664 physicians included in the analysis, 389 (23.4%) accounted for 83.6% of all trial enrollments. Similarly, 21 of 107 practices (19.6%) accounted for 80.5% of enrolled patients. Nearly 30% of physicians (494 of 1,664) did not enroll any patients during the study period.

The findings suggest that trial availability alone may not ensure patient access, with differences in physician engagement and practice-level research capacity potentially influencing which patients are offered opportunities to participate.

Physician and Practice Characteristics Influence Enrollment

To assess factors associated with participation, investigators used mixed-effects logistic regression models to examine patient-, physician-, and practice-level characteristics. Physician-level factors explained 12.3% of variation in clinical trial participation, while practice-level factors explained 15.1%. In comparison, observable patient-level characteristics accounted for 11.4% of variation.

The relative contribution of practice-level factors also increased over time. Their contribution to explainable variation rose from 13.7% during 2011 to 2014 to 21.9% during 2020 to 2024. Meanwhile, the contribution of patient-level characteristics declined from 14.0% to 8.6%, respectively.

Physician subspecialization and previous trial enrollment activity were associated with greater participation. Patients treated by physicians specializing in 1 to 2 cancer groups had higher odds of trial participation than those treated by physicians managing 5 to 7 cancer groups (OR, 4.11; 95% CI, 2.53-6.68; P =.002). Physicians treating 3 to 4 cancer groups also had higher enrollment odds (OR, 2.38; 95% CI, 1.37-4.14; P <.001).

Prior enrollment activity was another important factor. Patients treated by physicians who had enrolled other patients in trials during the preceding 2 years had higher odds of participation (OR, 1.58; 95% CI, 1.43-1.76; P <.001). This association demonstrated a dose-response pattern, with physicians who enrolled at least 3 patients in the preceding year having higher odds of participation (OR, 3.59; 95% CI, 2.99-4.31) than those who had not enrolled any patients.

At the practice level, high research engagement was associated with greater odds of participation (OR, 2.68; 95% CI, 2.12-3.39; P <.001).

Disparities Highlight Differences in Research Access

Patient-level characteristics were also associated with enrollment. Older age, lower area-level socioeconomic status, and poorer Eastern Cooperative Oncology Group performance status were associated with decreased odds of participation. Black patients had 26% lower odds of participating in clinical trials than White patients (OR, 0.74; 95% CI, 0.62-0.88; P <.001).

Practice-level socioeconomic differences were particularly pronounced. Practices serving the highest proportion of patients from socioeconomically disadvantaged areas had substantially lower odds of trial participation than other practices (OR, 0.42; 95% CI, 0.26-0.69; P =.002).

Additionally, investigators identified 17 practices with no observed trial enrollment, representing 3,257 patients. Although these patients had clinically comparable characteristics to the primary cohort, 42.6% were Hispanic and 46.9% lived in low-socioeconomic-status areas, compared with 5.5% and 35.2%, respectively, in the primary cohort.

Implications for Clinical Trial Access

The findings highlight opportunities to improve clinical trial participation by addressing barriers at the physician and practice levels. The concentration of enrollment among a relatively small proportion of physicians and practices suggests that expanding research engagement and infrastructure across more oncology settings could help broaden access. The authors point to potential strategies including physician mentorship, dedicated research contacts, staff support for trial-related testing, and tools to match patients with available studies.

“Oncologists across the country have long sensed that a patient’s chance of joining a clinical trial depends on which doctor and which clinic they see, and now we have data from more than 200,000 patients to show it. That is good news,” Changchuan Jiang, MD, MPH, of UT Southwestern and study lead author, stated in a news release. “Unlike a patient’s age or cancer type, a doctor’s trial habits and a clinic’s research support are things a health system can change.”

Additional investment in practices serving populations with lower socioeconomic status may also help address disparities in enrollment. These approaches could complement patient-focused efforts to improve representation in cancer clinical trials.

REFERENCES

1. 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

2. Which doctor and clinic a patient chooses is key to cancer clinical trial enrollment. News release. UT Southwestern Medical Center. November 10, 2026. Accessed November 11, 2026. https://tinyurl.com/37r36ymd