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Clinical Trials Without Zip Codes: Why Trial Access Maps onto Income, Not Just Biology

Clinical trials are supposed to be where the newest treatments become available before anywhere else. In practice, they're one of the clearest places where access to cancer care breaks along lines that have nothing to do with biology.

Start with how few patients get in at all: across cancer types, less than 1% of patients are enrolled in a clinical trial as part of their first-line treatment. For advanced prostate cancer specifically, it's about 2.6%. That's a narrow door under the best circumstances — and it isn't opening evenly.

Look at who walks through it. In one analysis of U.S. phase 3 randomized cancer trials, enrollees were 84.8% non-Hispanic white, compared to a U.S. Census estimate of 59.3% for that group. Another study found the median trial population was 88.7% white, versus 8.6% Black, 4.0% Hispanic, 1.4% Asian, 0.1% Native American, and effectively 0% Native Hawaiian and Pacific Islander patients. Researchers consistently link lower enrollment to the same cluster of factors: lack of insurance, lower income, less formal education, and — separately — geography, since trial enrollment is heavily concentrated at academic medical centers that aren't evenly distributed across the country.

None of that is a biological fact about who cancer affects. It's a description of who has a car, paid time off, insurance that covers travel to an academic center, and enough trust in the research system to say yes when asked. A patient priced out of the trial isn't just missing a chance at an experimental drug — they're also, structurally, being left out of the data that determines whether that drug works for people like them at all. The same disparities that keep patients out of trials are part of why treatments are later found to work differently across racial and socioeconomic groups: the population being studied never looked like the population that will eventually take the drug.

This is a solvable access problem, not just a research problem. Bringing trials to community hospitals instead of only academic centers, covering travel and lost wages for participants, and building trust with the communities who've historically been excluded — all of that is policy, not science. And it directly affects the science, because a trial without a representative population can't fully answer the question it set out to ask.