Cancer Clinical Trial Enrollment Has Recovered Despite the Ongoing COVID-19 Pandemic


Although cancer clinical trial enrollment plummeted during the initial wave of the COVID-19 pandemic, study results show that enrollment has rebounded over the past year.

Findings from a cohort study published in JAMA Network1 show that although cancer clinical trial enrollment decreased significantly during the first year of the COVID-19 pandemic, participation has been rebounding since the winter of 2020.

During the initial COVID-19 outbreak, from March 1, 2020, to April 25, 2020, a 9.0% model-estimated weekly reduction was reported in enrollments (relative risk [RR], 0.91; 95% CI, 0.89-0.93; P < .001), reflecting a reduction in the number of enrollments from an expected total of 1087 had the pandemic not occurred to a total of 730.

Enrollment subsequently recovered from April 26, 2020, to October 3, 2020, during which time a relative 4.0% model-estimated increase per week was reported in enrollments vs the prepandemic period (RR, 1.04; 95% CI, 1.03-1.05; P < .001). Although this still reflected a reduction in the number of enrollments from an expected total of 3079 had the pandemic not occurred to a total of 2295, by the end of the recovery period, weekly enrollments (n = 142) surpassed expected enrollments (n = 131).

However, trial enrollment decreased again during the winter between 2020 and 2021; though, the decrease was mild by only 2.0% each week (RR, 0.98; 95% CI, 0.97-0.99; P < .001).

“This finding suggests that clinical research rapidly adapted to the circumstances of enrolling and treating patients on protocols during the COVID-19 pandemic,” Joseph M. Unger, PhD, MS, lead study author and an associate professor in the Cancer Prevention Program Public Health Sciences Division at Fred Hutch, and coauthors, wrote in the study publication.

Cancer clinical trial participation underwent a steep decline during the initial wave of the COVID-19 pandemic.

To understand whether trial participation remained low or decreased further during the following months of the pandemic, investigators evaluated the experience of cancer clinical trial enrollment 1 year after the COVID-19 outbreak.

The cohort study evaluated initial enrollments to treatment trials and cancer control and prevention trials conducted by the SWOG Cancer Research Network between January 1, 2016, and February 28, 2021.

The onset and the apex of the initial COVID-19 wave was set as March 1, 2020, to April 25, 2020, respectively. The winter 2020 to 2021 wave was set as October 4, 2020, to January 23, 2021.

A total of 29,398 patients were enrolled: 24,034 before the pandemic and 5364 during the pandemic. The mean age of patients was 60.3 years. The study included 9198 patients (31.3%) 65 years of age or older, 17,199 female patients (58.6%), 3039 Black patients (10.8%), and 2260 Hispanic patients (7.9%).

Additional findings demonstrated that most enrollments (n = 19,451; 66.2%) were to treatment trials.

Moreover, enrollments comprised 77.3% of anticipated enrollments (n = 5364 of 6913; 95% CI, 70.5%-85.0%; P < .001). Specifically, enrollments comprised 54.0% of anticipated enrollments for cancer control and prevention trials (n = 1421 of 2641; 95% CI, 43.0%-67.0%; P < .001) and 91.0% of anticipated enrollments for treatment trials (n = 3922 of 4304; 95% CI, 81.0%-102.0%; P = .12).

Notably, the weekly relative reduction in enrollments during the initial COVID-19 wave for cancer control and prevention trials was 16.0% (RR, 0.84; 95% CI, 0.77-0.91; P < .001) vs the 6.0% weekly relative reduction reported for treatment trials (RR, 0.94; 95% CI, 0.92-0.95; P < .001; ratio of RRs, 0.90; 95% CI, 0.82-0.97; P = .01).

During the winter 2020 to 2021 period, the weekly relative reduction in enrollments was 3.0% (RR, 0.97; 95% CI, 0.95-0.99; P = .04) for cancer control and prevention trials vs 2.0% (RR, = 0.98; 95% CI, 0.97-0.99; P = .002) for treatment trials.

“Future studies should be conducted to evaluate the quality of data collection and the potential influence on clinical outcomes in patients with cancer enrolled in trials during the pandemic,” concluded the authors.


  1. Unger JM, Xiao H, LeBlanc M, et al. Cancer clinical trial participation at the 1-year anniversary of the outbreak of the COVID-19 pandemic. JAMA Netw Open. 2021;4(7):e2118433. doi:10.1001/jamanetworkopen.2021.18433

This article was originally published on OncLive as “Clinical Trials Prevail Despite the Continued COVID-19 Pandemic”

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