The impact of socioeconomic status on stage of cancer at diagnosis and survival: a population-based study in Ontario, Canada

Abstract

Background: Lower socioeconomic status (SES) is associated with worsened cancer survival. The authors evaluate the impact of SES on stage of cancer at diagnosis and survival in Ontario, Canada.

Methods: All incident cases of breast, colon, rectal, nonsmall cell lung, cervical, and laryngeal cancer diagnosed in Ontario during the years 2003-2007 were identified by using the Ontario Cancer Registry. Stage information is captured routinely for patients seen at Ontario's 8 Regional Cancer Centers (RCCs). The Ontario population was divided into quintiles (Q1-Q5) based on community median household income reported in the 2001 census; Q1 represents the poorest communities. Overall survival (OS) and cancer-specific survival (CSS) were determined with Kaplan-Meier methodology. A Cox model was used to evaluate the association between survival and SES, stage, and age.

Results: Stage at diagnosis was available for 38,431 of 44,802 (85%) of cases seen at RCCs. The authors observed only very small differences in stage distribution by SES. Across all cases in Ontario, the authors found substantial gradients in 5-year OS and 3-year CSS across Q1 and Q5 for breast (7% absolute difference in OS, P < .001; 4% CSS, P < .001), colon (8% OS, P < .001; 3% CSS, P = .002), rectal (9% OS, P < .001; 4% CSS, P = .096), nonsmall cell lung (3% OS, P = .002; 2% CSS, P = .317), cervical (16% OS, P < .001; 10% CSS, P = .118), and laryngeal cancers (1% OS, P = .045; 3% CSS, P = .011). Adjustments for stage and age slightly diminished the survival gradient only among patients with breast cancer.

Conclusions: Despite universal healthcare, SES remains associated with survival among patients with cancer in Ontario, Canada. Disparities in outcome were not explained by differences in stage of cancer at time of diagnosis.