Associations of social vulnerability with truncal and extremity melanomas in the United States

Prior studies in social determinants (SDoH) of truncal‐extremity melanomas (TEM) have analyzed race, income, and environmental factors relative to their effect on health disparities. However, they are limited by the narrow scopes of SDoH and study population, while lacking analyses of interrelational contribution of SDoH on TEM disparities.

demonstrated that racial and ethnic minorities have worse outcomes, despite the higher rates of incidence among older Caucasian populations. 2,3ior studies have demonstrated that various social determinants of health are associated with worsened outcomes.In turn, there is a question as to how social determinants may have an overlapping and multiplicative impact on outcomes. 4,5In recognition of this complex interplay between social determinants of health (SDH) and melanoma outcomes, health equity frameworks have started to recognize and address various structural, community, and individual determinants of health and develop unique solutions to systematically address SDH barriers. 6,7These social determinants of health include but are not limited to topics that fall into education access and quality, economic stability, social and community context, neighborhood and built environment, as well as healthcare access and quality.Within these frameworks, SDH indices have emerged as a potent tool, summarizing large-data survey information from the US Census and the American Community Surveys into quantitative, geospatial assessments of interloping SDH-factor status across varied sociodemographics.The CDC's Social Vulnerability Index (SVI) is a novel composite tool for SDH assessment that encompasses a wide variety of interloping SDH factors across themes of SES; minoritized race-ethnicity and English-language proficiency (ML); household composition and disability status (HH); and housing type & transportation (HT).Despite the availability of this tool, present literature lacks direct evidence of the inter-relational contribution of SDH on truncal and extremity-localized melanomas (TEM) and their related disparities across a wide spectrum of SDH.Furthermore, there is lacking evidence on the quantifiable impact of said SDH in real-world contexts.
To this end, this present study leveraged the SVI and SEER databases to principally analyze the amalgamated influence of varied SDH and their quantifiable impact on TEM care and prognosis across the United States.

| METHODS
This retrospective cohort study follows the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.No prior IRB/ethics committee approval or waiver of informed consent was needed; the databases queried consist of publicly available, deidentified data.

| Databases
The SVI was assessed for ranked scores across 15 different censuslevel social determinant variables within four themes of socioeconomic status (poverty, unemployment, income level, high school diploma status), minority status-language (minority status, proficiency with English), household composition (household members 65+ years, household members ≤17 years, disability status, single-parent status),  Histology subtypes were also categorized by ICD-O-3 codes.

| Statistical methods
Months survival within each histology subtype was analyzed by total SVI score and SVI-theme sub-scores.SVI scores were split into relative, equivalently sampled quintiles based on actual SVI scores within each histology subtype.The relative-SVI quintiles were delineated by "<20," "20-39.99,""40-59.99,""60-79.99,""80-99.99,"representing their relative percentiles per histology subtype (e.g., within disease A, patients with the lowest SVI scores are grouped into the "<20" quintile group).After separating patients into relative-SVI quintiles within each respective histology subtype, patients who were alive/lost upon last follow-up were excluded to extract patients who were dead upon last follow-up to isolate survival month values.
Among these total and SVI-theme quintiles, differences between the mean months survived for lowest and highest SVI-scored quintiles were calculated.Trend significance was assessed by linear regression across all data points against relative-SVI quintiles for months survival (i.e., not a trend through the baseline descriptive values), and boxplots were generated measuring the median, interquartile range (IQR), and 1.5 times the IQR.Means, standard deviations, and ranges for months surveyed per quintile were also calculated.Means, standard deviations, and ranges for actual total SVI scores and SVI-theme sub-scores were calculated per relativequintile group.
Statistical significance was set as p < 0.05.Two-sided p values were reported for analyses.All statistical analyses were conducted in R version 4.2.1.

| Histology subtype-specific trends in survival months by relative SVI percentile
Across all of the highest-sampled TEM subtypes, substantial decreases in mean months-survival between the lowest (i.e., least socially vulnerable overall) to highest (i.e., most socially vulnerable overall) total-SVI quintiles ranged from as high as 44.0%decrease (67.0-37.5 months) for epithelioid cell to as low as a 27.0% decrease (109.5-80.0months) for superficial spreading (Figure 1).These decreasing trends in months survived were statistically significant for 7 out of 13 TEM histology subtypes, which included epithelioid cell, lentigo maligna, nodular, spindle cell, superficial spreading, and NOS (p < 0.001 for all) (Figure 2).
Contributing to these total SVI vulnerability trends, increasing SVI-subtheme scores demonstrated differential levels of decreased survival association across TEM subtypes.Increasing vulnerability of socioeconomic status contributed the most, followed by equivalent contributions by minority-language status, housing-transportation, and household composition themes by association magnitude (Figure 1).

| Histology subtype-specific analyses of advanced staging by relative SVI percentile
For many TEM subtypes, patients with increasing total SVI vulnerability showed significantly increased odds of having an advanced staging on preliminary diagnosis for acral lentiginous (OR, 1.18; 95% CI, 1.02-1.36;p = 0.022), amelanotic (OR, 1.12; 95% CI, 1.02-1.24;p = 0.019), nodular (OR, 1.08; 95% CI, 1.03-1.13;p = 0.002), superficial spreading (OR, 1.08; 95% CI, 1.01-1.16;p = 0.045), and NOS (OR, 1.07; 95% CI, 1.06-1.09;p < 0.001) but not for melanomas in junctional nevi (OR, 0.34; 95% CI, 0.07-0.88;p = 0.022) (Table 3).| 547 Across these advanced-staging trends associated with increasing overall social vulnerability, increasing vulnerability in socioeconomic status, followed by household composition, housing-transportation, and then minority-language status proportionally contributed by magnitude to these decreases (Table 3).patients have decreased perception and knowledge of risk. 13,14With regard to health insurance, multiple studies have shown later staging of melanoma and other cancers on preliminary presentation for those who were uninsured or had Medicaid compared to patients with private insurance. 15,16 note, specific vulnerabilities of minoritized race-ethnicity and poor-English-proficiency showed significant but lower magnitude associations with observed TEM outcomes in this study.Given the significance, the trends observed in this present study remain consistent with prior isolated observations of racial-ethnic associations with melanoma disparities.For instance, Qian et al. showed that racial disparities have been worsening in the last decade despite universal improvement in melanoma outcomes. 4Brady et al. also recently reported significantly higher melanoma-specific death in non-Hispanic black patients compared to their non-Hispanic white counterparts. 3However, Rosenthal et al. showed in a multivariable analysis of California patients that race/ethnicity was not associated with survival disparities, but rather socioeconomic status was a strong predictor of melanoma-specific mortality. 17Our results remain consistent with these differences in social determinant impact but also provide added context in our analytical models by accounting for housing and transportation, as well as household composition.

| DISCUSSION
This present study also highlighted how social vulnerability was associated with decreased odds of receiving surgical treatment, with racial-ethnic minority vulnerabilities being the highest contributor by magnitude.Collins et al. noted that differences in outcomes after primary surgical resection between ethnic groups may be due to biological and genetic differences in tumors and their subtypes, although they do note the possibility that unmeasured factors such as SES, skin cancer awareness, and cultural and social values may be at play. 2 Some potential mechanisms at play in treatment receipt disparities include having limited access to a surgical oncologist or dermatologist, with barriers such as long travel distances, means of transportation, or even price of gasoline preventing timely care and treatment being suggested. 18Indeed, Onega et al. in 2008 showed that nonurban dwellers and residents in the South had the longest travel times to the nearest NCI Cancer Centre, a result that may in part underlie our findings. 19ile physical access to care may also partly explain why socially vulnerable patients present with more advanced stage melanoma at diagnosis, education and health literacy are also likely key contributors.1][22] Combined with decreased access to healthcare, it is no surprise that patients with increased social vulnerability only present for care after suspicious lesions have drastically worsened.Accordingly, accessible and evidence-based health literacy interventions that are readily understood by and available to patients may improve care and allow for early intervention. 23I G U R E 1 Relative decreases in survival period with increasing social vulnerability across melanoma subtypes.Relative differences between the lowest and highest vulnerability quintiles with each SVI-theme and total-SVI categories were taken within each melanoma subtype.
F I G U R E 2 Survival period differences with increasing social vulnerability across melanoma subtypes.Across equivalently sampled quintiles based on total SVI score, patients who suffered mortal outcomes were assessed for their median, IQR, 1.5×IQR, and mean months of survival.Linear regression was performed across increasing vulnerability quintiles to assess trend significance of differences.Maroon diamonds indicated the mean.
T A B L E 2 Surgical receipt trends with increasing social vulnerability.Finally, we found that minority status-language and housing transportation were important contributors to disparities in care.This suggests that continued improvements in physician-patient communication through tailored patient-centered resources and local outreach by surgery and dermatology groups into the communities they serve are important avenues to improve disparities. 24Social support measures that improve access to healthcare, such as transportation to and from clinics and hospitals, will also improve T A B L E 3 Advanced-staging on first presentation trends with increasing social vulnerability.6][27][28] Existing research on intersectionality has been challenging and limited, and as noted by Herari and Lee. 29 Note: Univariate logistic regressions assessing odds of whether or not late-stage (reference being "Stage I, II, III") was first diagnosed on melanoma presentation based on increasing levels of social vulnerability in overall or SVI-themecategories. Reference levels for total and SVI themes were the lowest vulnerability quintile and ordinally increased with higher levels of vulnerability for comparators.
and housing-transportation (multi-unit structure, mobile homes, crowding, no vehicle, group quarters), as well as a differentially weighed, composited total SVI score.SVI-theme sub-scores are differentially weighed to formulate the total composite score and are assigned different weights based on sociodemographic-census data of the designated area.Total and SVI-theme scores are based on relative social vulnerabilities of a particular census tract among all 72 158 US census tracts, ranging from 0 to 1 with 0 representing the lowest social vulnerability and 1 representing the highest.The National Cancer Institute-Surveillance, Epidemiology, and End Results Program (NCI-SEER) database contains national data sets of patient variables, pathological characteristics, treatment modalities, and prognostic outcomes.Months survival represents the period of active follow-up among patients who would only suffer a mortal outcome.Staging was based on SEER-designated variables and recoded under American Joint Committee on Cancer, 6th Edition (AJCC-6) classifications.Stage at presentation was categorized as early-stage (I, II, III) and advanced stage (IV).Outcomes of interest included indicated primary surgery occurrence, which represents whether patients received surgical resection for their primary malignant melanoma diagnosis.Specific SEER-provided variables were used for determining whether surgical resection was indicated.SVI scores were abstracted and matched to SEER-patient data based on county-of-residence at the time of diagnosis.Countyassigned scores were generated by weighted score means per population density of each census tract within the county.

2. 2 |
Population definitions SEER was queried for adult (20+ years) patients diagnosed with malignant melanomas between 1975 and 2017.Truncal and extremity regions were isolated using International Classification of Diseases for Oncology, Third Edition (ICD-O-3) topographic codes.

T A B L E 1
Patient characteristics by social vulnerability score.
Univariate logistic regressions assessing outcomes whether or not primary surgery was received based on increasing levels of social vulnerability in overall or SVI-theme categories.
a By American Joint Committee on Cancer, 6th Edition (AJCC-6).
By using a theoretical and analytical framework centered upon intersectionality to understand cancer disparities, it may be possible to develop new solutions in a patient-centered and inclusive manner moving forward.