Triple-Negative Breast Cancer Trials Leave Millions of Women Too Far From Care

For women diagnosed with triple-negative breast cancer, the most aggressive and hardest-to-treat form of the disease, the promise of a clinical trial often depends on something as mundane as a map. A new nationwide analysis published in Breast Cancer Research and Treatment has found that the geography of hope is starkly uneven: more than three-quarters of all U.S. counties have no active triple-negative breast cancer treatment trial at all, and the counties left behind are precisely those where patients face the greatest barriers to care. The study, led by researchers at The University of Texas MD Anderson Cancer Center in collaboration with the American Society of Clinical Oncology and other institutions, is the first to map the geographic distribution of triple-negative breast cancer trials against the demographic and social characteristics of the communities where women actually live.

Triple-negative breast cancer, which lacks the three molecular targets exploited by modern targeted therapies, accounts for roughly 10 to 15 percent of all breast cancers but is diagnosed at more advanced stages and offers fewer effective treatment options than other subtypes. It disproportionately strikes women under 40, women with BRCA1 mutations, and Black women, who are diagnosed at twice the rate of women of any other racial or ethnic background. Because clinical trials have driven nearly every recent advance in the disease’s treatment, including the landmark pembrolizumab studies that reshaped care within the last five years, equitable access to those trials is not an abstract concern. It is the mechanism by which scientific progress translates into longer lives.

To build their national picture, the researchers queried ClinicalTrials.gov as of September 30, 2024, sifting through all 510,397 registered studies to isolate active phase II and phase III interventional treatment trials specific to triple-negative breast cancer. After excluding non-cancer studies, studies without U.S. sites, and trials no longer open to enrollment, they identified 108 active trials, 58 for metastatic disease and 50 for non-metastatic disease, supported by 1,230 trial sites across the country. Each site was assigned to a U.S. county through spatial join analysis, and the resulting tabulations were overlaid with county-level data from the U.S. Census Bureau, the U.S. Department of Agriculture’s rural-urban continuum codes, the Centers for Disease Control and Prevention’s Social Vulnerability Index, and the U.S. Climate Vulnerability Index’s baseline health vulnerability scores.

The headline numbers are sobering. Of the nation’s 3,144 counties, 76.2 percent had no available triple-negative breast cancer trial whatsoever. Only 12.4 percent had exclusively federally sponsored trials, 9.7 percent had both federally and non-federally sponsored trials, and a mere 1.7 percent relied solely on industry or other non-federal sponsors. Yet the picture is not uniformly bleak: 78 percent of the roughly 124 million U.S. women aged 18 and older lived in a county with at least one trial available, and another 17 percent had access in an adjacent county. The problem is concentrated in specific, identifiable populations, and the study’s county-level breakdown reveals exactly where the trial network frays.

Rural America sits at the sharpest edge of the disparity. Trials were available in just 9.8 percent of rural counties compared with 47.0 percent of metropolitan counties, a difference the authors report as highly significant. And among the rural counties that did host trials, 80 percent offered exclusively federally sponsored studies, compared with only 42 percent of metropolitan counties with trials. In other words, the federal clinical trials infrastructure, including the National Cancer Institute’s National Clinical Trials Network, is effectively the sole lifeline keeping rural women connected to experimental treatments. Any contraction in federally sponsored research, the authors warn, would have uniquely devastating consequences for rural patients, whose cancer mortality rates, including ten-year breast cancer mortality, are already known to exceed those of their urban counterparts.

Health vulnerability tells a parallel story. Counties in the highest quartile of the Climate Vulnerability Index’s baseline health vulnerability measure, reflecting burdens of chronic disease, limited access to care, and poorer preventive health, were significantly less likely to have any available trial: 88.3 percent had none, compared with 72.2 percent of counties in the lower three quartiles. Among counties with trials, 73 percent of the most health-vulnerable depended exclusively on federal sponsorship, versus 50 percent of less vulnerable counties. Social vulnerability showed a similar, though somewhat attenuated, gradient, with 78.6 percent of the most socially vulnerable counties lacking any trial. This mirrors a broader pattern in American oncology, where 94 percent of all cancer trial sites are located in areas more affluent than the national average.

Race and ethnicity shaped the map as well. Among counties with predominantly non-Hispanic White populations, 75.8 percent had no triple-negative breast cancer trial, compared with 79.1 percent of predominantly Hispanic counties, 81.5 percent of predominantly Black counties, and a striking 96.9 percent of predominantly American Indian and Alaska Native counties. But the researchers caution that county-level racial predominance does not necessarily reflect where members of each group actually live. When they analyzed access at the population level instead, most Black women, 82.1 percent, and Hispanic women, 86.5 percent, resided in counties with an available trial, while access dropped to 63.5 percent among American Indian and Alaska Native women and rose to 93.5 percent among Asian and Pacific Islander women. The divergence between county-level and population-level measures, the authors argue, underscores the need to evaluate trial access through both lenses.

Regional disparities compound the inequity. Ten percent of women in the South, more than five million people, lacked access to a triple-negative breast cancer trial in either their home county or any neighboring county, compared with just 1 percent of women in the Northeast. This is particularly troubling because the South carries the heaviest burden of new triple-negative breast cancer diagnoses in the country, accounting for 40 percent of cases, more than the Northeast and West combined. Two-thirds of Southern counties had a trial available, versus 87 percent of counties in the Northeast and West. Meanwhile, metastatic trials, the studies most relevant to patients with advanced disease, were scarcer than early-stage offerings: only 63 percent of trial sites had metastatic trials, and just 9.4 percent of metastatic trial sites offered four or more options, limiting both proximity and choice for the women who need trials most urgently.

The study’s findings arrive amid a broader reckoning with the representativeness of cancer research. Trial participants have historically been younger, healthier, and less racially, ethnically, and geographically diverse than the patients who ultimately receive the resulting therapies. Prior work by some of the same investigators found that 70 percent of all U.S. counties lacked any cancer treatment trial and that 51 percent had neither research nor oncology care sites. Survey data cited in the new paper show that only 37 percent of patients actively undergoing cancer treatment are willing to travel for a trial, yet more than half of women with metastatic breast cancer report driving over an hour to reach a trial site. When comparable trial options are available to rural and urban patients alike, studies suggest, the survival gap between them narrows or disappears, making geographic access a modifiable determinant of outcome.

The authors point toward concrete remedies: pragmatic and decentralized trial designs that reduce the burden of participation, expanded eligibility criteria to ensure results generalize to real-world populations, and technologies such as telemedicine and remote monitoring that can decouple enrollment from physical proximity. They also emphasize the outsized importance of sustained federal investment in programs like the NCI Community Oncology Research Program and the National Clinical Trials Network, which extend trial infrastructure into community settings. The analysis has limitations, including its reliance on manually entered ClinicalTrials.gov data and its descriptive, county-level design, which cannot establish causation or capture individual enrollment decisions. Still, as the first study to chart the geography of triple-negative breast cancer trials against the demographics of the women they are meant to serve, it offers government agencies, industry sponsors, and hospital systems a data-driven roadmap for deciding where the next trial site should open, in a disease where novel treatment strategies are urgently needed and every mile between a patient and a protocol can matter.

Subject of Research: Geographic access to triple-negative breast cancer clinical trials in the United States

Article Title: Geographic access to triple negative breast cancer clinical trials: are trials located near patients?

Article References: Amin, L. B., Kirkwood, M. K., Levit, L. A., Balogh, E. P., Waterhouse, D. M., Unger, J. M., Garrett-Mayer, E., & Chavez-MacGregor, M. (2026). Geographic access to triple negative breast cancer clinical trials: are trials located near patients?. Breast Cancer Research and Treatment, 219(3), Article 22. https://doi.org/10.1007/s10549-026-08084-3

Image Credits: AI Generated

DOI: 10.1007/s10549-026-08084-3

Keywords: triple-negative breast cancer, clinical trials, health disparities, geographic access, rural health, health equity, ClinicalTrials.gov, National Cancer Institute, social vulnerability, breast cancer mortality, trial sponsorship, United States