Site enrollment

Why clinical trial sites miss enrollment targets

By TrialNotice · Updated
Research site manager looking at a monitor showing an enrollment bar chart falling below a red target line
Short answerMost sites that miss enrollment targets are short on a steady inflow of eligible patients, not effort. Tufts CSDD's study of nearly 16,000 sites found 11% of sites in a trial enroll zero patients and 37% under enroll, while 52% meet or exceed their targets. Protocols have grown stricter over time, which makes a site that depends on one patient source especially exposed.

How many clinical trial sites miss enrollment targets?

Tufts CSDD analyzed nearly 16,000 sites in Phase II and III trials. In a typical trial, 11% of sites fail to enroll a single patient, 37% under enroll, 39% meet their targets, and 13% exceed them (Tufts CSDD via Fierce Biotech). In North America, 13% of sites failed to enroll a single patient (Applied Clinical Trials).

11%
of sites in a trial enroll zero patients
37%
of sites under enroll
52%
meet or exceed their targets

This is not new. Getz noted the share of sites that never enroll a patient has not changed in 20 years (Clinical Leader).

Is enrollment concentrated in a few sites?

Yes. A Phesi analysis of 173 cancer trials found 19% of investigator sites contributed less than 3% of enrolled patients, while the top 16% of sites contributed 54% (Applied Clinical Trials). Sponsors notice which group a site falls into when they assign the next study.

Why do sites fall short?

  • Stricter protocols. Between 2002 and 2012, the total number of eligibility criteria in a typical Phase III protocol rose from 31 to 50 (Tufts CSDD, Getz). More criteria means more patients screened for every one enrolled.
  • One patient source. A site that relies only on its own records runs out of candidates once that panel is screened.
  • No physician referral pipeline. Physicians refer less than 0.2% of their patients into trials, mainly because they lack study information and time (Tufts CSDD). Most sites never reach them systematically.

What does an under enrolling site cost the sponsor?

Phesi estimates that with a $40,000 site activation cost and $3,000 per month to manage a site, a 30 month study where a site enrolls just one patient costs $130,000 for that site alone (Applied Clinical Trials). That cost is part of why sponsors track site performance so closely. For the bigger picture, see what one day of delay costs a trial.

What can a site control to hit enrollment?

  1. Add a second and third patient source before the first one runs dry.
  2. Reach the physicians who treat your study population near the site with specific study information.
  3. Make referral easy and close the loop so referring physicians stay engaged.
  4. Track which outreach produces screened patients, and shift effort there.

Read how to recruit more patients for a clinical trial for the full plan.

Get your study in front of the right local physicians

TrialNotice builds a physician referral pipeline around one active study. We identify relevant local physicians within driving distance of your site, send study aligned direct mail, follow up by email and LinkedIn, track engagement with recipient level QR codes, and route warm responses into your site team's workflow.

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Sources

  1. Tufts CSDD, patient recruitment and retention practices study (Jan 2013), via Fierce Biotech
  2. Applied Clinical Trials, "Enrollment Performance: Weighing the Facts"
  3. Clinical Leader, "Why Is Study Start Up Still So Inefficient?" (interview with Ken Getz, Tufts CSDD)
  4. Ken Getz, Tufts CSDD, "The Cost of Clinical Trial Delays" (CTTI presentation)
  5. Applied Clinical Trials, "Phesi Report: Assessing Single Patient Investigator Sites in Cancer Clinical Trials"
  6. Applied Clinical Trials, "Tufts CSDD Study Explores Low Recruitment Rates"

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