Background: The social vulnerability index (SVI), developed by the CDC, is a novel social disadvantage metric based on comprehensive data from the U.S. Census Bureau American Community Survey. It includes 15 different social variables organized into the subthemes of socioeconomic status (SES), household composition & disability, minority status & language, and mobility & transportation. For each geographic unit (county or census tract), the SVI dataset generates a composite score that ranges from 1% to 100% with a higher score correlating with increased vulnerability. Recently, some research groups have been applying the SVI as a risk stratification tool to evaluate the impact of social determinants of health (SDOH) on health outcomes in cancer patients.
Objective: To investigate the innovative use of the SVI in examining health disparities in cancer patients, and to use the framework of the cancer care continuum to identify future research opportunities.
Methods: A systematic search was performed in MEDLINE, Embase, Web of Science Core Collection, Scopus, and PubMed for relevant English articles published from database inception to November 22, 2021. Included articles used the SVI to examine any outcomes in cancer patients. This review followed the PRISMA guidelines.
Results: Of the 216 unique records retrieved, 21 articles were identified as meeting inclusion criteria. Along the cancer care continuum, four studies applied the SVI to examine geographic disparities in potentially cancer-causing exposures (e.g., oncogenic viruses, environmental contaminants); six in cancer diagnosis (e.g., all-stage, early-stage, late-stage); twelve in cancer treatment (e.g., surgery receipt, chemotherapy receipt, transplant receipt); seven in treatment recovery (e.g., post-operative complications, readmission rates); one in cancer survivorship care (e.g., follow-up visits); and two in end-of-life care (e.g., hospice utilization, hospice timing). No studies were identified as addressing the secondary prevention, or early detection, of cancer (e.g., cancer screening).
Discussion: A majority (52.4%) of included studies stratified patients into SVI quartiles for analyses with the bottom 25% labeled as "low SVI" (low vulnerability) and the top 25% as labeled "high SVI" (high vulnerability). Seven studies examined other area-level SES or SDOH measures such as employment status, median household income, education, language, and rurality. One study also examined individual-level SDOH measures. Overall, the included studies demonstrated that with increasing SVI, patients were more likely to receive neoadjuvant chemotherapy, less likely to undergo surgical resection at a high-volume hospital, more likely to experience postoperative complications, less likely to achieve postoperative textbook outcomes, and more likely to receive fragmented postoperative care.
Conclusion: Actionable interventions based on objective metrics could be formulated by determining the relative impact of SVI variables and/or subthemes on health outcomes. Among cancer patients, the SVI could be used to evaluate all aspects of the cancer care continuum, particularly early detection. Future research may also utilize the SVI to examine health disparities in other patient populations, including racial/ethnic minority patients.
Abbreviations: SVI, social vulnerability index; CDC, Centers for Disease Control and Prevention; SES; socioeconomic status; SDOH, social determinants of health; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses
