How Accessible are Clinical Trials for Skull Base Disorders within the United States?

Skull base disorders (SBDs) have gained attention within the medical community due to the rising incidence and complexity of treatment. SBD risk has been correlated with low socioeconomic status (SES), among other factors.[1] [2] Importantly, low SES is linked to reduced geographic accessibility to health care services,[3] including clinical trials, a disparity accentuated by the coronavirus disease 2019 (COVID-19) pandemic. To elucidate the concept of geographic accessibility within SBDs, we performed a retrospective trend analysis, evaluating geographic access to SBD clinical trials across the United States for a period of 20 years.

The clinical trial data were obtained from the ClinicalTrials.gov Application Programming Interface (API) by using a comprehensive keyword search strategy related to SBDs. Next, we measured SBD population demographics from the Census.gov API. Lastly, we calculated distances between ZIP code population centers and clinical trial locations using the Haversine formula[4] and then assessed changes in accessibility over time starting from 2005 until 2024.

We identified 18,750 SBD clinical trials, 12,044 of which were initiated before 2020 and 6,706 after. At least one clinical trial was hosted at 2,442 unique ZIP codes, with an average of 7.86 trials per each of these zip codes. Linear regression analysis demonstrated a slight increase in the average distance to the nearest clinical trial over time (slope = 1.87 km/year), with substantial increases from post-COVID, although this trend was not statistically significant (p = 0.0739; [Fig. 1]). The population coverage at various distance thresholds over time was also evaluated ([Table 1]). When assessing population coverage before and after 2020, no significant reduction in accessibility postpandemic was found (t-test statistic = 1.47, p = 0.205). However, the number of clinical trials decreased consistently from pre- to post-COVID, with 2,997 trials in 2019 and just 586 by 2023. While this reduction may reflect a disruption in research activities due to the pandemic, other factors may also have played a role, such as rising clinical demands on health care providers detracting from clinical trial initiation, shifts in research priorities, or decreased governmental or private funding for trials during this period.

Table 1 Percent population coverage within distance thresholds

Year	10 miles	20 miles	30 miles	40 miles	50 miles	60 miles	70 miles	80 miles	90 miles	100 miles
2005	54.04	72.8	81.1	85.9	88.97	91.19	93.1	94.77	95.9	96.89
2006	53.24	71.48	79.56	84.7	88.11	90.65	92.81	94.24	95.59	96.41
2007	54.53	70.86	78.96	84.01	87.74	90.34	92.75	94.42	95.68	96.81
2008	63.85	78.88	85.62	89.78	92.52	94.55	95.7	96.72	97.46	97.97
2009	55.01	72.64	80.45	85.39	88.72	91.34	93.12	94.62	95.76	96.54
2010	53.62	71.29	79.64	84.58	88.2	90.77	92.93	95.11	96.98	98.07
2011	49.35	67.55	75.68	81.27	84.93	87.55	89.76	91.96	93.45	94.62
2012	51.32	68.34	76.17	81.86	85.69	88.58	90.96	92.68	94.25	95.7
2013	47.93	66.21	74.3	79.51	83.33	86.73	89.43	91.08	92.96	94.24
2014	67.97	82.59	88.85	92.78	94.96	96.56	97.44	98.08	98.58	98.83
2015	71.87	85.02	90.72	94.15	95.96	97.28	98.03	98.6	98.98	99.21
2016	56.26	73.92	81.07	86.48	89.85	92.24	94.06	95.31	96.15	96.79
2017	67.54	81.06	86.85	90.91	93.33	95.15	96.38	97.16	97.69	98.17
2018	51.84	68.88	76.54	80.96	84.23	86.82	89.11	90.93	92.83	94.33
2019	66.22	79.74	85.8	89.53	92.25	94.42	96.13	97.27	98.2	98.68
2020	70.7	82.97	88.76	92.43	94.73	96.2	97.24	97.91	98.49	98.97
2021	58.59	72.61	80.23	84.64	87.87	90.09	92.13	93.88	95.46	96.72
2022	44.39	60.61	68.57	73.37	77.34	80.46	82.8	84.77	86.93	89.35
2023	49.41	65.33	72.08	77.44	81.22	84.3	87.02	89.53	91.39	93.18
2024	33.23	48.45	56.74	61.86	66.56	70.29	73.96	78.11	81.01	83.79

Fig. 1 Average distance to clinical trials over time.

The results are consistent with previous studies demonstrating a correlation between geographic accessibility and health care facility use.[5] The coverage analysis shows decreasing accessibility to trial sites, particularly within shorter distances (i.e., 10 and 20 miles), suggesting that these locations are becoming less accessible for a larger portion of the population. Additionally, the average distance to SBD clinical trials is increasing while the total number of such trials is decreasing with time, reflecting the fragility of the clinical trial infrastructure in the wake of the COVID-19 pandemic.[6] Although many of these trends did not reach statistical significance, they suggest the need for ongoing efforts to expand the geographic footprint of clinical trials and ultimately alleviate patient travel burdens. One of these efforts may include increased funding dedicated to SBD clinical trials from public sources, such as the National Institute of Health, which would provide greater resources to establish studies in underserved or rural areas. Another effort may be stronger collaborations with local health care institutions, which could facilitate access to more clinical trial sites and diversify the patient population. Relatedly, clinical trials that focus on more common SBDs, such as meningiomas or vestibular schwannomas, are likely to face fewer geographic access disparities, as a larger number of patients would reside closer to trial sites.[7]

These findings have critical implications for skull base surgery, as enhanced access to clinical trials is essential for patients with SBDs to benefit from novel therapies and techniques. Improved geographic accessibility may boost patient participation, potentially leading to the earlier adoption of innovative procedures and improved clinical outcomes. Future research should explore geographic accessibility to other health care services in skull base surgery, particularly during challenging circumstances, emphasizing the exploration of strategies that alleviate the disparities present in health care access for patients with SBDs.

Publication History

Article published online:
18 November 2024

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