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

Background: 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. Methods: This retrospective cohort study of adult TEM patients (1975–2017) assessed linear regression trends in months of survival, as well as logistic regression trends in advanced presenting stage, surgery, and chemotherapy receipt across TEM subtypes with increasing overall social vulnerability and vulnerability in 15 SDoH variables grouped into socioeconomic status (SES), minority-language status (ML), household composition (HH), and housing-transportation (HT) themes measured by the SVI. SVI measures are ranked/compared across all US counties for relative vulnerability in a specific SDH and their total composite while accounting for sociodemographic–regional differences. Results: Across 325 760 TEM patients, increasing overall social vulnerability demonstrated significant decreases in the survival period for 7/13 TEM histology types (p < 0.001), with relative decreases in the survival period as high as 44.0% (67.0–37.5 months) for epithelioid cell. SES and HH were the highest-magnitude contributors to these overall trends. For many patients with TEM, increased odds of advanced presenting stage (highest with acral-lentiginous: odds ratio [OR], −1.18; 95% confidence interval [CI], 1.02–1.36), decreased odds of indicated surgery receipt (lowest with amelanotic, 0.79; 0.71–0.87), and increased odds of indicated chemotherapy (highest with melanoma in giant nevi: 1.50; 1.01–2.44) were observed; SES and ML followed by HH and HT contributed to these trends. Conclusions: There were detriments in TEM care & prognosis in the United States with increasing social vulnerability. Identifying which SDH quantifiably are associated more with disparities in interrelational, real-world contexts is important to provide nuance to inform future research and initiatives to address TEM disparity.