Association of Neighborhood Social Vulnerability With Metastatic Cancer at Diagnosis.

[BACKGROUND] Relationships between socioeconomic factors and metastatic cancer at diagnosis have not been well studied. Using CDC's Social Vulnerability Index (SVI) we studied the association of metastatic cancer at initial diagnosis with 16 social factors and their interaction with insurance status.

[METHODS] California and Texas cancer registries, merged with the SVI database, were used to identify adult patients diagnosed with breast, colorectal, liver, lung, ovarian, pancreatic, or prostate cancer from 2015 to 2019. To determine the association of SVI with metastatic cancer at initial diagnosis, multivariable binary logistic regression analyses were performed.

[RESULTS] Of the 654,016 patients included, 149,476 (21.5%) were diagnosed with metastatic cancer at diagnosis. Overall, the adjusted odds of metastasis at diagnosis increased by 5% for every 10 unit increase in SVI. Stratified by cancer type, the odds (95% confidence interval) of metastatic cancer at diagnosis were: breast 1.04 (1.03-1.05), colorectal 1.01 (1.01-1.02), liver 1.03 (1.02-1.05), lung 1.01 (1.01-1.02), pancreatic 1.02 (1.01-1.03), prostate 1.06 (1.05-1.07). Interaction analysis of insurance with SVI revealed that the marginal effect of the association between SVI and the risk of metastasis at initial diagnosis increased most substantially as SVI increased for patients who had insurance. It was relatively constant for uninsured and Medicaid patients, who had the overall highest average risk.

[CONCLUSIONS] Increased neighborhood social vulnerability is associated with an increased risk of metastatic cancer at initial diagnosis. While uninsured patients or those on Medicaid had a higher risk, patients with other insurance types experienced the largest increases in risk associated with increasing SVI.