Outcomes Among Patients With Colon Cancer Living in Neighborhoods With Persistent Poverty

Patients with cancer living in persistent poverty (PP) are at risk for worse oncologic outcomes. Existing welfare interventions typically focus on current poverty and may not benefit patients in PP if the underlying mechanisms are unique; thus, modifiable targets are needed to inform future policy efforts.

To compare clinical outcomes for patients diagnosed with colon cancer based on the share of census tracts per zip code that were in PP at the time of diagnosis and to explore 2 potential mechanisms connecting PP and disease-specific mortality.

This retrospective cohort study using data from a statewide cancer registry included all patients diagnosed with colon cancer in California from 2017 to 2020. Patients with multiple malignant tumors and patients diagnosed based on only their death certificate were excluded. Data were analyzed from February 2024 to February 2025.

Proportion of census tracts per zip code designated as being in PP at the time of diagnosis (0, 0.01-0.25, 0.26-0.50, and >0.50).

The primary outcome was disease-specific mortality. Secondary outcomes included overall mortality, stage at diagnosis, and receipt of guideline-concordant care. Fine-Gray competing risk survival models were used to calculate risk-adjusted mortality and to evaluate the relative contribution of access to care and quality of care as potential mediators of the association between PP and disease-specific mortality. Charlson comorbidity indices ranged from 0 to 14, with higher values indicating higher comorbidity.

In total, 20 015 patients (mean [SD] age at diagnosis, 65.9 [14.0] years; 51.3% male) met inclusion criteria, and the majority (66.3%) resided in zip codes with no PP. Patients living in areas with higher PP ratios were younger (eg, mean [SD] age at diagnosis, 64.3 [14.1] years for >50% PP vs 66.3 [14.1] years for no PP), more likely to identify as Hispanic (eg, 45.5% for >50% PP vs 19.2% for no PP) or non-Hispanic Black (eg, 15.7% for >50% PP vs 4.9% for no PP), and had higher Charlson comorbidity indices (eg, mean [SD] score, 1.3 [1.8] for >50% PP vs 1.2 [1.7] for no PP). After adjustment for demographic and clinical variables, higher shares of PP were associated with higher rates of disease-specific mortality: hazard ratios, 1.20 (95% CI, 1.07-1.36) and 1.19 (95% CI, 1.01-1.42) for PP ratios 0.26-0.50 and higher than 0.50, respectively. Health care practitioner density did not appear to mediate this association. However, adjusting for the receipt of guideline-concordant care affected both the magnitude and the statistical significance of the model, suggesting potential mediation.

In this cohort study, living in PP was associated with disease-specific mortality among patients diagnosed with colon cancer. The Persistent Poverty Initiative presents a unique opportunity to improve our understanding of PP and to support efforts to extend treatment to all US residents with cancer.