A Blood Test Report Should Not Easily Bar a Patient: FDA Revamps Cancer Trial Eligibility Thresholds

Entry into cancer clinical trials is often guarded by a series of blood and biochemical test values. These thresholds were originally intended to protect participants, but when applied too rigidly, they may exclude people who could participate safely and make it difficult for trial results to show how a drug will perform in more complex patients once it enters routine medical care.

The U.S. Food and Drug Administration (FDA) recently finalized guidance on laboratory value eligibility criteria for cancer trials, recommending that sponsors avoid exclusion criteria without sufficient justification. The document was formally announced in the Federal Register on July 28. The guidance was revised from a draft issued in April 2024, and the FDA said it had considered public comments, with the final version primarily adding clarifying revisions.

The guidance focuses on later-stage cancer trials. The FDA believes that criteria such as blood cell counts and liver and kidney function should be tailored to the investigational drug, cancer type, anticipated safety risks, and trial objectives, rather than directly copying the conservative thresholds used in early-stage trials. As clinical experience grows, research teams should also regularly review whether exclusion criteria remain necessary.

Abnormal values do not necessarily indicate higher risk. Malignancy itself, comorbidities, age, and physiological differences among populations can all affect test results. The FDA specifically cites the Duffy-null phenotype as an example: people with this phenotype may have lower absolute neutrophil counts without a corresponding increase in infection risk. Relying on a single threshold alone could therefore result in unnecessary exclusion.

The document also highlights the chain reaction between trial design and the usability of evidence. Overly strict eligibility criteria may slow recruitment, limit patients’ access to investigational treatments, and create a disconnect between trial participants and the population that will actually use the drug after approval. More representative later-stage trials can help physicians and regulators determine whether efficacy and risks extend to patients who are common in clinical practice but more medically complex.

The laboratory value guidance is one of three cancer trial documents finalized by the FDA at the same time. The other two address performance status, and washout periods and concomitant medications, respectively. This set of reforms continues the FDA’s direction since 2019 of reducing restrictive criteria that lack scientific justification and has also been incorporated into the U.S. Department of Health and Human Services’ Operation Trialblazer initiative.

However, the guidance reflects the FDA’s current policy thinking and is not legally binding in itself, nor does it mean that all laboratory thresholds should be lowered. Strict criteria may still be reasonable for certain drugs that could cause bone marrow suppression or organ toxicity. The real change will depend on whether sponsors can provide risk-based justification, continuously update trial designs, and enable review committees to make verifiable judgments balancing safety and representativeness.