Low Physician Density, High Social Vulnerability Predict AlloHCT Gaps Across the US

Lower physician density and higher social vulnerability index (SVI) scores each independently predicted higher unmet need for allogeneic hematopoietic cell transplantation (alloHCT) across US counties, identifying several states where patients were at risk for alloHCT challenges, according to findings published in JCO Oncology Practice.¹

In the exploratory retrospective analysis, Texas, North Carolina, Florida, Nevada, and Georgia were identified as at-risk states for alloHCT access challenges, based on aggregated SVI, Centers for Medicare & Medicaid (CMS) Physician Compare (now Care Compare), and 2018 to 2022 alloHCT unmet need data across all US counties. In county-level models across all US counties, lower physician density (b = −10.102; P <.001) and higher SVI (b = 13.799; P <.001) predicted higher unmet need, with socioeconomic status (b = 12.295; P <.001) and housing/transportation vulnerability (b = 4.370; P =.016) also predicting higher unmet need in sensitivity analysis.

“I think the states that pop up as highly at risk and the areas that we're highlighting here are prime for deeper analysis and deeper understanding of what's going on in those populations,” Samantha E. Watters, PhD, MPH, principal provider education and research partner at NMDP and first author of the article, said in an interview with Targeted Oncology^TM.

Barriers to Transplant Access

Although donor availability itself is no longer a primary obstacle to alloHCT, according to Watters, a range of barriers continue to limit which patients are able to access transplant. The procedure is expensive and time consuming, often requiring patients to relocate near a transplant center for up to 100 days following the procedure, a requirement that disproportionately affects patients who are financially strained, lack a caregiver, do not have reliable transportation, have limited health literacy or English proficiency, or lack strong health insurance coverage. Physical proximity to specialty hematology-oncology and transplant providers can be similarly limited depending on where a patient lives, Watters said.

Older age and comorbid conditions have historically posed a barrier to transplant, though Watters noted that reduced-intensity conditioning regimens have made age alone far less of an obstacle than in the past. She observed that this shift has not always been consistently communicated to community-based diagnosing providers who may not routinely refer patients for transplant.

Combining Available Datasets to Evaluate Unmet Need

Watters and her colleagues used the CIBMTR (Center for International Blood and Marrow Transplant Research) database to calculate alloHCT utilization and estimated need per 100,000 county population over a 5-year period. Physician desnity was defined as hematology-oncology and HCT physicians per 10,000 population using Care Compare data from the CMS, and SVI, a composite index scored from 0 to 1 across socioeconomic status, household characteristics, race/ethnicity, and housing/transportation themes, was calculated at the county level using data from the CDC Agency for Toxic Substances and Disease Registry.

“We have these 3 variables that we're working with to better understand how they relate to each other and to get a more holistic picture of access to care,” said Watters.

Investigators divided physician density and unmet need into low (≤ 50th percentile) and high (> 50th percentile) categories and used multivariable linear regression to assess predictors of unmet need.

Counties with high SVI and unmet need combined with low physician density were flagged as at risk (396 counties with an estimated 51.9 million residents). States with more than 1.7 million people living in at-risk counties were then evaluated at the state level; 5 states with at least 2 of the 3 variables in the at-risk range, Texas, North Carolina, Florida, Nevada, and Georgia, were deemed at risk overall.

At-Risk States Analysis

Within the 5 at-risk states, bivariate analysis found only physician density to be significantly associated with unmet need; in sensitivity analysis, total SVI (b = 13.111; P <.001), race/ethnicity vulnerability (b = 17.913; P <.001), and housing/transportation vulnerability (b = 14.164; P <.001) also emerged as significant predictors. Texas accounted for 23.5% of the total population living in at-risk counties nationally, which was consistent with broader findings on access challenges to medical care. The authors observed that restricted Medicaid expansion and coverage in Texas and other states was a potential contributing factor, as was distance to transplant centers in rural areas.

“The physician density piece came through very consistently as hugely significant across all of the analyses,” Watters said in the interview. “It’s not always the case…because the difference between urban and rural centers is pretty vast. You might, in an urban area, have a lot of physicians, but those physicians may not be as accessible because of other social factors...Whereas when you go to rural areas, you have this physical distance that you’re trying to overcome when you’re trying to access care, and you have these physician deserts.”

As a secondary analysis of population-level data, these findings may miss the intricacies of barriers at an individual level, but the study is “giving a more holistic picture of how these different barriers can interact with each other and where in the country geographically we should be digging a little bit deeper and looking a little bit more closely at how to improve access to care,” Watters said.

The striking link to physician density could be employed to identify where the gaps are for some transplant centers; she suggested that it could guide where to place new satellite sites and community outreach clinics to target key at-risk communities.

Growing Outreach to Expand HCT Access

Overcoming these barriers requires a collaborative effort between transplant centers, nonprofits, and other groups that support patients in need, Watters said. Improvements in conditioning and HLA matching have dramatically expanded eligibility and donor suitability, but these advances may not be as top of mind for community healthcare providers who treat fewer patients with blood cancers regularly.

Steps are being taken to address these problems both by nonprofits and health systems. Watters pointed to NMDP’s Pathways to Transplant program, which connects community hematology-oncology providers with transplant centers and offers free HLA typing in the community, as one existing resource, and cited outpatient transplant models and shared posttransplant care arrangements between transplant centers and local practices, such as one developed at Dana-Farber Cancer Institute, as approaches that could extend care into at-risk communities.³ The ACCESS initiative from NMDP and the American Society for Transplantation and Cellular Therapies is also aiming to address these barriers not only through awareness but by improving resource allocation.²

Identifying the specific factors standing between patients and alloHCT is still an ongoing process; the study authors noted that as a population-level ecological analysis, the findings may not represent individual patient-level barriers, and that the regression models explained only 20% to 25% of the variance in unmet need on average, indicating additional unmeasured factors likely contribute to access gaps.¹

“The biggest message I have is to advocate for building that strong relationship between the community and your transplant center,” Watters said, emphasizing that the earlier the communication about a transplant consultation takes place, the more opportunities there are to address nonclinical barriers.

“All these nonprofits have resources to overcome care challenges, financial burdens, transportation, housing, and things like that…but having more time to do that is so critical,” she added. “All of that can open the door where otherwise, without that connection, a conversation may just never happen.”

Although many factors can keep patients from getting alloHCT at the time when it can make the most difference in their disease outcomes, oncology care teams that proactively seek out support for their patients can ensure that these specialized resources are accessible. 

“I think it’s really about building those relationships and those strong connections,” Watters concluded. “If the transplant center knows about the patient early, and if NMDP knows about the patient early, then we can help provide patient navigation and support to overcome those barriers as much as possible.”

REFERENCES

1. Watters SE, Meyer CL, Preussler JM, Senneka MKS, Auletta JJ, Borzekowski DLG. Access challenges in allogeneic hematopoietic cell transplant: identifying at-risk US states by exploring social vulnerability, physician density, and unmet need. JCO Oncol Pract. Published online June 29, 2026. doi:10.1200/OP-25-01138

2. Auletta JJ, Khera N, DeMartino P, et al. Assessing Medicaid coverage for hematopoietic cell transplantation and chimeric antigen receptor T cell therapy: a project from the American Society for Transplantation and Cellular Therapy and the National Marrow Donor Program ACCESS Initiative. Transplant Cell Ther. 2023;29(11):713-720. doi:10.1016/j.jtct.2023.08.007

3. Abel GA, Kim HT, Zackon I, et al. Shared local oncology care after allogeneic hematopoietic cell transplantation: a randomized clinical trial. JAMA Oncol. 2025;11(3):268-275. doi:10.1001/jamaoncol.2024.5786