Objectives:

Under-served groups are populations unrepresented or disengaged from medical research or services despite a disproportionately high healthcare burden. Under-served groups may be directly (age, pregnancy as examples) or indirectly excluded (provision of written information in one language only as example) from trial enrolment by strict eligibility exclusions. The purpose of our study was to assess eligibility criteria in published phase III breast cancer clinical trials to determine whether they excluded under-served groups either directly, or indirectly.

Study design and setting:

Medline was searched for phase III randomised controlled trials evaluating interventional drugs for breast cancer in high-impact journals published between January 1^st, 2010 and December 31st, 2020. 5133 eligible trials were returned and 40 selected, by simple randomization, for inclusion.

Results:

All 40 trials had multiple exclusions that affected recruitment of under-served groups. Clinical or scientific rationale for the recorded inclusion and exclusion criteria was under-reported in 39 of 40 trials.

Conclusions:

Clinical trial eligibility criteria exclude under-served groups from breast cancer trials. Trialists should provide a justification for each eligibility criterion and funders, reviewers, ethics committees, and others should demand one. Without this under-served groups will remain just that: under-served.