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

Abstract

Background

Geographic proximity to clinical trials is a major barrier to trial participation, but geographic access to trials has not been specifically characterized for triple-negative breast cancer (TNBC). We evaluated the geographic distribution of TNBC treatment trials across U.S. counties and examined associated social and demographic characteristics.

Methods

All trials registered on ClinicalTrials.gov as of September 30, 2024 (n = 510,397) were queried, and active phase II and III TNBC treatment trials were identified through keyword searches. County-level population estimates from the 2018–2022 U.S. Census Bureau 5-year estimates and county adjacency data were used to evaluate trial availability and geographic access. Trial availability was examined according to sponsorship, rurality, health vulnerability, race and ethnicity, and U.S. region.

Results

We identified 108 active TNBC trials, including 58 (54%) for metastatic and 50 (46%) for non-metastatic disease. Overall, 76% of U.S. counties had no TNBC trials, 12% had exclusively federally sponsored trials, 10% had both federally and non-federally sponsored trials, and 2% had only non-federally sponsored trials. Trial availability was significantly lower in counties with the highest health vulnerability and in rural counties, which were more likely to rely exclusively on federally sponsored trials. Counties with predominantly Black, Hispanic, and American Indian and Alaska Native populations were less likely to have TNBC trials than predominantly non-Hispanic White counties. Women in the South were more likely than women in the Northeast to have no TNBC trial available in either their county of residence or a neighboring county.

Conclusions

TNBC clinical trials are geographically concentrated across the United States, with substantial disparities in access affecting rural and highly vulnerable counties, counties with predominantly racial and ethnic minority populations, and women living in the South. Federally sponsored trials may play an important role in supporting trial availability in underserved areas. Expanding the geographic distribution of TNBC trials may help improve equitable access to clinical trial participation.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1007/s10549-026-08084-3.

Introduction

Breast cancer is the second leading cause of cancer death and the most common cancer among women in the United States (U.S.), accounting for 32% of all new cancer diagnoses for women in 2024¹. Across all breast cancer subtypes, mortality has decreased over the past decade [1]. Most of the reduction in breast cancer mortality is attributable to advances in all stages of disease treatment, including reducing disease recurrence, with an additional smaller mortality reduction afforded by early detection through screening [2]. Triple-negative breast cancer (TNBC), an aggressive breast cancer subtype, continues to be diagnosed at more advanced stages and has fewer effective therapies available than other breast cancer subtypes [1]. TNBC accounts for approximately 10–15% of all breast cancers and is more common among women who are under age 40, who are Black, or who have a BRCA1 mutation [3]. Clinical trials have been critical to improving the available treatment options for TNBC, with groundbreaking studies changing the TNBC treatment paradigm within the last 5 years [4, 5]. Unfortunately, the observed mortality benefit from treatment advances in TNBC has not been distributed evenly across the population, reflecting the worse cancer outcomes among patients who are Black, living in rural areas, or residing in areas with high levels of socioeconomic deprivation [6].

Clinical trials should be representative of the population to ensure that the benefits of novel treatment strategies are effective for the diverse population of individuals with cancer, including women living with TNBC. Unfortunately, clinical trials are often unrepresentative of patients receiving cancer care in the U.S., with trial participants more likely to be younger, healthier, and less racially, ethnically, and geographically diverse [7–11]. This disconnect has prompted collective calls to action to improve clinical trial representation by identifying and addressing the multifactorial barriers to equitable trial enrollment [12–16]. One such barrier is the geographic proximity of patients to clinical trial sites [17–19]. While geographic distance to trial centers has hindered cancer clinical trial enrollment generally and among women with breast cancer [17], it remains understudied among women with TNBC. In this study, we analyzed data available from ClinicalTrials.gov to describe the national landscape of TNBC treatment trials. The primary objective of this study was to evaluate the association of number of available TNBC treatment trials in a county with demographic and social characteristics of that county.

Methods

Data sources

We queried ClinicalTrials.gov, an international registry of clinical trials maintained by the U.S. National Library of Medicine [20], to identify TNBC treatment trials. Trial data were supplemented with county-level data from the U.S. Census Bureau [21], including female population counts among adults aged ≥ 18 years and measures of predominant racial and ethnic composition, rural status from the U.S. Department of Agriculture [22], Social Vulnerability Index (SVI) scores from the Centers for Disease Control and Prevention (CDC) [23], and baseline health vulnerability from the U.S. Climate Vulnerability Index (CVI) [24]. SVI scores are derived from 16 U.S. Census Bureau American Community Survey variables related to socioeconomic status, racial and ethnic minority status, household characteristics, housing type, and transportation [23]. Baseline health vulnerability scores from the CVI are derived from data from multiple sources related to physical and mental health, access to care, chronic and infectious diseases, disease prevention, and child and maternal health. Rurality and social and health vulnerability were included in the analysis to represent areas where women might face additional barriers to accessing trials or meeting trial eligibility criteria due to comorbid conditions.

Identifying and characterizing TNBC trials

To identify TNBC-specific treatment trials, we searched all studies registered on ClinicalTrials.gov as of 9/30/2024 (n = 510,397; Supplemental Figure 1) [20]. Variables of interest were study identification number, title, description, overall status (e.g., recruiting, completed), disease type, study type (e.g., investigational, observational), sponsor name, sponsor class, phase, and geographic location of study sites.

Non-cancer studies (n = 499,504) and studies without U.S. sites (n = 54,630) were removed. To focus on trials currently open to enrollment and thusly available to patients across the country, we excluded trials in “Completed,” “Terminated,” “Withdrawn,” “Suspended,” or unknown status (n = 33,392), leaving trials in “Recruiting,” “Not yet recruiting,” “Active, not recruiting,” and “Enrolling by invitation” status (n = 13,188). We included only interventional treatment trials in Phase II, II/III, or III (n = 4,209) by removing observational and expanded access studies (n = 2,043), basic science and other non-treatment-related purposes for studies (n = 2,529), and Phase I, I/II, IV, and unknown Phase studies (n = 4,407). We identified trials containing “triple negative” or “TNBC” listed in the title or disease variable or with TNBC described via biomarkers (e.g., evidence of human epidermal growth factor receptor 2 (HER2) negativity, estrogen receptor (ER) negativity, and progesterone receptor (PR) negativity within the title or disease variables).

These resulting TNBC trials were categorized into metastatic and non-metastatic trial categories based on whether the terms “metastatic” or “advanced” appeared in the title or description variables. To create a sponsor type classification, we consolidated National Institutes of Health and Network sponsors into a federal group and kept the remaining industry and other categories. We also categorized trials by time since initiation– 0–2 years, 2–5 years, and 5 or more years—relative to date of data capture.

Geospatial analysis of TNBC trial sites and county tabulations

Trial site locations associated with the 108 TNBC trials of interest were mapped using ArcGIS Pro 3.2.1. Trial sites were categorized as having 1–3 trials or 4 or more available trials to approximate a limited versus expanded trial portfolio at that site. We superimposed these sites with demographic information. We created maps that examined the overall distribution of TNBC trial sites, as well as maps that examined the distribution of metastatic and non-metastatic trials. We also assigned a U.S. County to each site through spatial join analysis to create trial tabulations by county.

County information for each TNBC site was processed in R 4.3.3, with each trial counted once per county (including representation in ≥ 1 counties). County-level tabulations were produced. Consistent with a prior analysis, we assessed trial availability per county by number of TNBC trials and also by adjacency to counties with trials [18]. These tabulations were appended with population counts of women aged ≥ 18 years for all 3,144 U.S. counties and population summaries were prepared by county trial status. We examined differences in trial availability by county metropolitan status (rural and urban) and county predominant race or ethnicity using chi squared and Fisher’s exact methods, respectively. Statistical significance was defined as a p value ≤ 0.05. Counties with fourth quartile social vulnerability and fourth quartile baseline health vulnerability rankings across all U.S. counties were considered highly vulnerable and assessed for trial availability.

Results

Characteristics of TNBC treatment trials

A total of 108 active TNBC studies were included in the analysis (Supplemental Figure 1), 58 (54%) of which were metastatic trials and 50 (46%) of which were non-metastatic trials (Table 1). Most studies were Phase II (n = 87, 80.6%) and the remainder were Phase III (n = 21, 19.4%). There was a total of 1,230 U.S. study sites with TNBC trials. Of them, 708 (58%) had active Phase II and III trials, 454 (37%) had only Phase III trials, and the remaining 68 (6%) had only Phase II trials. A total of 1,150 (93%) trial sites had non-metastatic trials available and 780 (63%) had metastatic offerings. Just 73 of the 780 (9.4%) metastatic trial sites had 4+ available metastatic trials. Counties were categorized according to the number of available TNBC trials (1–3 vs. ≥4) and overlaid with county-level demographic data to visualize the geographic distribution of metastatic (Fig. 1A) and non-metastatic (Fig. 1B) trial availability relative to women aged ≥ 18 years. Metastatic TNBC trials were less geographically available than non-metastatic trials. At the trial-site level, non-metastatic TNBC trial portfolios were generally larger, with 485 of 1,150 non-metastatic trial sites (42%) offering four or more non-metastatic trials.

Table 1.

Characteristics of TNBC trials active in the U.S

		Number of Trials (%)
Overall		108
Cancer Extent	Metastatic	58	(54)
	Non-Metastatic	50	(46)
Participant Sex	All	86	(80)
	Female	22	(20)
Phase	Phase II	87	(81)
	Phase III	21	(19)
Trial Sponsor	Federal Government	10	(09)
	Industry	28	(26)
	Othera	70	(65)
Time Since Trial Initiation	0–2 years	36	(33)
	2–5 years	30	(28)
	5+ years	42	(39)
Trial Recruitment Status	Active Not Recruiting	53	(49)
	Not Yet Recruiting	5	(05)
	Recruiting	50	(46)

Data Source: ClinicalTrials.gov, query date 9/30/2024

^a Includes institutions, non-governmental research networks, and philanthropy organizations

Fig. 1.

Geographic distribution of active metastatic and non-metastatic TNBC clinical trials relative to the female population aged ≥ 18 years in the United States. Panel A shows counties with active metastatic TNBC trials, with small red circles indicating counties with 1–3 available metastatic trials and large red circles indicating counties with four or more available metastatic trials. Panel B shows counties with active non-metastatic TNBC trials, with small yellow circles indicating counties with 1–3 available non-metastatic trials and large yellow circles indicating counties with four or more available non-metastatic trials. County-level shading represents the number of females aged ≥ 18 years, with darker shading indicating higher population density. Data sources: ClinicalTrials.Gov [20] and the U.S. Census Bureau [21]

Concerning trial initiation period, we observed that one in three TNBC trials opened recently (i.e., within 2 years of data capture; n = 36), while the plurality of trials, on the other hand, opened more than 5 years before (n = 42, 39%). Recently opened trials were available at 900 (73%) of sites. A total of 1099 (89%) of sites had trials opened within the last 5 years, leaving 11% of sites with only TNBC trials initiated more than 5 years prior.

County and regional distribution of trials

Overall, 78% of women aged ≥ 18 years (n = 101,670,016) lived in a county with a TNBC trial available (Table 2). An additional 17% (n = 22,297,521) of women did not have a trial in their county of residence but had one available in a neighboring county. Trial availability differed by U.S. Census Bureau-designated geographic region, with 5,094,914 of 50,165,908 women in the South (10%) lacking access to a TNBC trial in either their county of residence or an adjacent county, compared with 169,482 of 23,424,029 women in the Northeast (1%).

Table 2.

Female population aged ≥ 18 Years by availability of TNBC trials according to U.S. Region*

Data sources: U.S. Census Bureau [20] and ClinicalTrials.gov [21]

* Regions defined as midwest: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin; Northeast: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont; South: Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia; and West: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming

Among counties with predominantly non-Hispanic White populations, 75.8% had no TNBC trials available, compared with 79.1% of predominantly Hispanic counties, 81.5% of predominantly Black counties, and 96.9% of predominantly American Indian and Alaska Native counties (Figs. 2A, C; p < 0.001). TNBC trial availability differed significantly according to rural status (p < 0.001), with 90.2% of rural counties lacking any available TNBC trials compared with 53.0% of metropolitan counties (Fig. 2C). To complement the county-level analyses, we examined TNBC trial availability by race and ethnicity among women aged ≥ 18 years regardless of county racial or ethnic predominance (Supplementary Table 1). Most Black (82.1%) and Hispanic (86.5%) women resided in counties with an available TNBC trial, whereas access was lower among American Indian and Alaska Native women (63.5%). Trial availability within a county was highest among Asian and Pacific Islander women (93.5%).

Fig. 2.

Distribution of U.S. counties with active TNBC clinical trial sites by trial number and county-level race, ethnicity, and rural–urban status. Panel A shows counties with active TNBC clinical trials, with small black circles indicating 1–3 active trials and large black circles indicating four or more active trials, overlaid on county-level predominant race and ethnicity. Panel B shows counties conducting TNBC clinical trials, with small black circles indicating 1–3 active trials and large black circles indicating four or more active trials, overlaid on county-level metropolitan (purple) versus rural (green) classification based on rural–urban continuum codes. Panel C shows the distribution of counties by trial status (4+ trials, 1–3 trials, or none) by county characteristic (predominant race and ethnicity, rural status). Data source: U.S. Census Bureau [20], ClinicalTrials.gov [21], U.S. Department of Agriculture [22]. *** p < 0.001 by Fisher’s exact and chi-square methods, respectively. County color determined by quintile of female aged 18+ population. Data sources: ClinicalTrials.Gov and the U.S. Census Bureau

Distribution of trials by sponsor

The landscape of available TNBC trials varied according to trial sponsor (Figs. 3A, B). Among all U.S. counties (n = 3,144), 12.4% had exclusively federally sponsored TNBC trials available, 9.7% had both federally and non-federally sponsored trials available, and 1.7% had exclusively non-federally sponsored trials available; 76.2% had no available TNBC trials. Counties with both federally and non-federally sponsored trials were concentrated around major population centers, whereas counties with federally sponsored TNBC trials, including those conducted by the National Cancer Institute’s (NCI) National Clinical Trials Network (NCTN), were more broadly distributed throughout the country. Among the 748 counties with available TNBC trials, 389 (52%) had exclusively federally sponsored trial offerings. These counties were home to approximately 21 million women aged ≥ 18 years, representing 16% of the adult female population. Counties with exclusively non-federally sponsored trials were uncommon and did not demonstrate a distinct geographic pattern.

Fig. 3.

Distribution of U.S. counties with active TNBC clinical trials by sponsor type and county-level vulnerability characteristics. Panel A displays the geographic distribution of counties with active TNBC clinical trials, stratified by trial sponsor type and county characteristics. Panel B presents the corresponding quantitative percentages of counties with active trials by sponsor type across county characteristic strata. Counties in the highest quartile (Q4) of social vulnerability Index (SVI) and health vulnerability are designated as the most vulnerable. SVI scores are derived from 16 U.S. Census Bureau American community Survey variables encompassing socioeconomic status, racial and ethnic minority status, household composition, housing type, and transportation. Baseline health vulnerability scores from the climate vulnerability Index (CVI) are derived from multi-source data reflecting physical and mental health, access to care, chronic and infectious disease burden, disease prevention, and child and maternal health. Orange indicates counties with only federally sponsored trials, green indicates counties with only non-federally sponsored trials, red indicates counties with both federally and non-federally sponsored trials, and white indicates counties with no active trials. Data source: ClinicalTrials.gov [20], U.S. Census Bureau [22], social vulnerability Index scores from the Centers for disease Control and Prevention (CDC) [23], U.S. Climate vulnerability Index [24]. * p < 0.05 by chi-square analysis

Trial availability stratified by county-level social characteristics

Trial availability differed significantly according to county-level social vulnerability, health vulnerability, and rural status (Fig. 3B). Among counties in the highest quartile of social vulnerability (n = 786), 78.6% had no available TNBC trials compared with 75.4% of counties in the lower three quartiles combined (n = 2,358) (p < 0.05). Counties in the highest quartile of health vulnerability (n = 786) had lower trial availability, with 88.3% lacking any available TNBC trials compared with 72.2% of counties in the lower three quartiles (p < 0.001). Trial availability also differed according to rural status, with TNBC trials available in 9.8% of rural counties compared with 47.0% of metropolitan counties (p < 0.001). Among rural counties with available TNBC trials, 80% had exclusively federally sponsored trial offerings.

Discussion

This study examined the relationship between the geographic distribution of active TNBC clinical trial sites and the demographic and social characteristics of the surrounding areas. We identified several important features of the national TNBC trial landscape. At the time of our query on 9/30/2024, metastatic TNBC clinical trials were less broadly available than earlier stage, non-metastatic trials. Just 63% of TNBC trial sites had metastatic trial offerings as compared to 93% of the sites offering non-metastatic trials. Even among sites with metastatic trials available, only 6% of TNBC trial sites had 4 or more clinical trials. This suggests most women with metastatic TNBC have limited ability to access a clinical trial site close to home, which may be limiting recruitment to these trials and slowing treatment advances that are so urgently needed. In one survey of patients being actively treated for cancer, only 37% expressed willingness to travel for a clinical trial, but over half of women with metastatic breast cancer reported needing to drive over an hour to reach a clinical trial site [15, 17]. Our study identified that for TNBC in particular, metastatic trial offerings are not available at many clinical trial sites and even when available, are more likely to be limited in number, potentially restricting patient eligibility. This raises concern that any individual woman with TNBC seeking a clinical trial may have a particularly difficult time finding an appropriate trial for her disease near her home.

An important finding of our study is that TNBC trials were less likely to be located in counties with racial and ethnic minority-predominant populations. Specifically, counties with predominantly Black, Hispanic or Latino, and American Indian or Alaska Native populations had fewer available TNBC trials than counties with predominantly non-Hispanic White populations. However, county-level racial and ethnic predominance does not necessarily reflect where members of each racial and ethnic group reside. To better characterize population-level access, we performed an additional analysis evaluating trial availability by race and ethnicity among women aged ≥ 18 years regardless of county racial or ethnic predominance. Although predominantly Black, Hispanic, and American Indian or Alaska Native counties were less likely to have available TNBC trials, most Black (82.1%) and Hispanic (86.5%) women resided in counties with available TNBC trials, whereas access remained lower among American Indian and Alaska Native women (63.5%). These findings suggest that geographic inequities in trial placement may affect racial and ethnic groups differently and highlight the importance of evaluating both county-level and population-level measures of access. Geographic availability of clinical trials may represent one of several factors contributing to persistent disparities in breast cancer outcomes [1, 25]. While White women have experienced a 43% reduction in the breast cancer death rate since 1990, this rate decreased by only 31–32% among Hispanic and Black women, and remained unchanged among American Indian and Alaska Native women [1]. Moreover, TNBC disproportionately affects Black women, who are diagnosed with the disease at twice the rate of women of any other racial or ethnic background [26]. Black women also have higher mortality from TNBC, even after adjustment for sociodemographic, clinicopathologic, and county-level factors [25]. Prioritizing equitable access to and representation in therapeutic clinical trials remains essential to ensuring that advances in TNBC treatment benefit all patient populations.

We identified regional differences in TNBC trial site distribution. Two-thirds of Southern U.S. counties had a metastatic or non-metastatic TNBC trial available, compared to 87% of counties in the Northeast and the West. This is concerning because the Southern U.S. carries the highest burden of new TNBC diagnoses, representing 40% of the cases, more than the burden of new TNBC diagnoses in the Northeast (18.2%) and West (19%) combined [26]. In addition to regional variation, we examined urban versus rural differences in trial availability. Overall, 17% of TNBC trial sites were located in rural counties where 14% of the U.S. populations lives [27]. Patients living in the rural U.S. are known to have higher rates of cancer mortality, including breast cancer 10-year mortality [28], than their urban counterparts. The availability of clinical trials, including TNBC trials, is key to narrowing this mortality disparity. [6, 29].

Notably, we observed that patients living in rural areas benefit disproportionately from federally sponsored TNBC trials as compared to their urban counterparts, who have greater access to trials from a variety of sponsors. 80% of rural counties with TNBC trial sites had exclusively federally sponsored clinical trials. In metropolitan counties, only 42% of counties with TNBC trial sites were entirely reliant on federally sponsored trials. This suggests that any reduction in federally sponsored trial availability would confer uniquely devastating impacts on TNBC clinical trial access for rural Americans, whose outcomes are known to be worse [6]. Access to cancer clinical trials is particularly important for patients living in rural areas, as data suggests when comparable trial options are available for patients in rural and urban areas, we do not see the same disparities in outcomes [29]. Our findings highlight the importance of ongoing investment in programs, such as the NCI Community Oncology Research Program (NCORP) and National Clinical Trials Network (NCTN), which aim to improve patient access to and geographic reach of cancer clinical trials [30].

We also evaluated trial availability in the most socially vulnerable counties in the U.S [31]. The majority of U.S. cancer clinical trial centers, which account for 94% of all U.S. cancer trial sites, are located in more affluent areas than the U.S. average [19]. TNBC trials generally followed this broader trend [32, 33]. Counties in the highest health vulnerability quartile (Q4) were significantly less likely to have an available TNBC clinical trial than those in the remaining three quartiles (Q1–Q3; p < 0.001). As with rural counties, highly health vulnerable counties were especially dependent on federally sponsored clinical trials. Among counties with available TNBC trials, 50% of those in the lower three quartiles of health vulnerability relied exclusively on federally sponsored trials, compared with 73% of counties in the highest health vulnerability quartile. This finding emphasizes the outsized role federally sponsored trials play in preserving access to TNBC clinical trials for millions of Americans. Finally, we noted that 39% of included TNBC trials were initiated 5 or more years before data extraction. However, trial duration should be interpreted cautiously, as nearly half of included studies (49%) were classified as “Active, Not Recruiting,” suggesting that prolonged study duration may reflect ongoing follow-up rather than continued patient enrollment. Consequently, study duration alone cannot be used to assess trial accrual performance.

The issues raised in this study of TNBC trials are pronounced, but not unique, within the national landscape of cancer trials. These findings build on a 2024 geographic analysis of treatment trials across cancer types, which established that 70% of all counties lacked any trials and 51% of all counties had neither research nor oncology care sites [18]. Counties with few TNBC trial offerings, counties with cancer trial infrastructure but no TNBC trials, and those with care sites but no trials represent areas for potential expansion of the TNBC trial network. As the cancer community pursues trial modernization efforts, strong consideration should be given to the development and activation of pragmatic, decentralized, and simplified clinical trial designs. In addition, expanded eligibility is key to ensure generalizability [13]. Facilitating the incorporation of new technologies including, but not limited to, telemedicine and remote monitoring to improve patient access to research should also be considered [34, 35]. As clinical trials have added millions of life-years to patients with cancer over the past 45 years, efforts to include more Americans in trial populations via these mechanisms should be a high priority for the oncology community [30].

While ClinicalTrials.gov offers a centralized view of the present TNBC trial landscape in the U.S., relying on these data has limitations. ClinicalTrials.gov requires manual data entry from sponsors, which is vulnerable to omission or misclassification. Some analyses have found data quality discrepancies across specific trials when compared to other trial documents [36, 37]. In addition, while geographic location of clinical trial sites is a critical factor for trial enrollment, there are many other variables relevant to recruiting representative clinical trial populations, including eligibility criteria, cost, transportation, and time commitment, among others [9, 14, 38, 39]. In addition, our study is descriptive in nature, evaluating county-level availability of TNBC clinical trials rather than individual-level access, enrollment, or participation. Consequently, the relationships observed between county characteristics and trial availability should not be interpreted as causal and may be affected by unmeasured confounding factors. Finally, our analysis focused on the adult female population and therefore does not specifically address geographic access to TNBC clinical trials among men with breast cancer. While TNBC is rare in men, access to clinical trials within this population warrants future investigation.

To our knowledge, this is the first study evaluating the geographic distribution of TNBC treatment trials relative to the demographic characteristics of the U.S. population. This study provides novel insights into the role of a previously under-explored variable in perpetuating ongoing disparities in clinical trial enrollment for this particularly high-mortality malignancy. We identified that metastatic TNBC clinical trials are less widely available than early-stage treatment trials, that counties with racial and ethnic minority-predominant populations were less likely to have available TNBC trials, although population-level access differed across racial and ethnic groups, and that rural and high health vulnerability counties are deeply reliant on federally sponsored trials to maintain any TNBC trial access. Our findings may help government, industry, and hospital-based systems prioritize their limited resources to preserve and expand clinical trial access for women with TNBC, a disease in which novel treatment strategies are urgently needed.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

LBA, MKK, LAL, EPB, DMW, EGM, JMU, MCM, participated in the writing and approval of the manuscript. LBA, MKK, LAL, EPB, MCM, EGM, participated in conceptualization. LBA, MKK, LAL, EPB, MCM, EGM, participated in interpretation of the data. MKK participated in data curation and formal analysis.

Funding

This work was supported by grants from Susan G. Komen; SAC220221; Breast Cancer Research Foundation (BCRF); 23-190.

Data availability

The datasets supporting these findings are available at www.ClinicalTrials.gov and www.Census.gov.

Declarations

Ethical approval

This study used publicly available, de-identified data from ClinicalTrials.gov and publicly available county-level datasets. No human participants were directly involved, and no individually identifiable information was collected or analyzed. Therefore, this study did not constitute human subjects research and did not require Institutional Review Board review or approval.

Human ethics and consent to participate

Not applicable.

Prior presentations

This work was presented in part in a poster presentation at the 2025 ASCO Annual Meeting.

Competing interests

MCM has served as consultant for Astra Zeneca, Roche, Novartis, Pfizer and Exact Sciences. The rest of the authors report no competing interests to declare.