Impact of Social Vulnerability Index and Travel Distance on Access to Chimeric Antigen Receptor T-Cell Therapy

Introduction: Chimeric antigen receptor T-cell (CAR T) therapy has transformed the treatment of many relapsed and/or refractory hematological malignancies. However, the CAR T-cell therapy is limited to a few academic centers, requiring patients to be referred to these larger academic centers. As a result, access to this life-saving treatment remains unequal. As the only CAR T-cell therapy center in Arkansas, we planned to assess the impact of socio-economic factors and travel distance on access to CAR T-cell therapy.

The social vulnerability index (SVI), developed by the Centers for Disease Control and Prevention, is a good indicator of the socio-economic situation of a community. It is calculated based on 15 variables, and each county is given a score ranging from 0 to 1, with values closer to 1 indicating higher social vulnerability. Previous studies have found an association between SVI and various health-related outcomes.

Methods: In this study, we evaluated the impact of SVI and travel distance on access to CAR T-cell therapy and their subsequent outcomes. The study was approved by our institutional review board. All patients listed to receive CAR T-cell therapy on or before April 30, 2024, were included in the study. The date they were added to the list with the intent to give CAR T-cell therapy was taken as the date of listing.

Results: 291 patients were listed to receive CAR T-cell therapy. The most common malignancies were multiple myeloma (64%) and diffuse large B-cell lymphoma (29%). 176 (60%) patients were from Arkansas, and 114 (40%) were from other states. There were 108 (37%) females. Of the 291 patients listed, 222 (76%) identified as white, and 53 (18%) identified as African American (AA).

The median time from diagnosis to listing was 44.1 months. At a median follow-up of 15.8 months from listing, only 145 of the 291 (50%) patients received CAR T-cells. Among patients who received CAR T, the median duration from listing to apheresis and listing to CAR T-cell infusion were 1.1 (range: 0.0-21.4) months, and 3.1 (range: 1.2-23.0) months, respectively. The mean SVI for all patients listed for CAR T-cell therapy, patients from Arkansas, and patients from other States were 0.633, 0.632, and 0.634, respectively. The median travel distance to our center for patients from Arkansas was 83 (range: 2-238) miles.

The mean SVI of patients who received CAR T-cell therapy was 0.632 (95% CI: 0.595-0.668), compared to 0.634 (95% CI: 0.598-0.670) in patients who did not get CAR T-cell therapy (p = 0.92). In patients from Arkansas, the mean SVI (p = 0.98) and mean travel distance (p = 0.45) of patients who got CAR T-cell therapy were not significantly different from those who did not get CAR T-cells. There was no significant difference in SVI (p = 0.89) or travel distance (p = 0.73) in Arkansan patients who died versus those still alive at the last follow-up.

The mean SVI of the white patients was 0.601 compared to 0.755 for AA patients, which was significantly different (p < 0.001). 117 of the 222 white patients received CAR T-cell therapy, compared to 19 of the 53 AA patients, which was significantly different with a z-statistic of 2.23 (p = 0.03). There was no significant difference in the SVI of AA patients who got CAR T versus those who did not (p = 0.769).

Patients from Arkansas who were listed for CAR T-cell therapy were divided into two groups - those with an SVI greater than or equal to 0.632, and those with an SVI less than 0.632 (0.632 being the mean SVI of listed Arkansas patients). The median duration from diagnosis to listing for CAR T-cell therapy was higher in the group with a higher SVI (30.0 vs. 14.7 months, p < 0.01). We found no similar difference in the median time from listing to CAR T-cell infusion (p = 0.21). Kaplan-Meier survival analysis showed no significant difference in survival outcomes between the two groups (p = 0.31).

Conclusion: Only 50% of the patients listed for CAR T-cell therapy actually received it. Patients from higher SVI counties had a longer wait time from diagnosis to listing for CAR T-cell therapy. However, once listed, SVI and travel distance did not significantly influence access to CAR T-cell therapy or overall survival outcomes. White patients had a significantly higher chance of getting CAR T-cell therapy after listing compared to AA patients. This study highlights the non-disease related factors that could influence access to CAR T-cell therapy. Larger studies are needed to validate our findings.